\input texinfo
@c
@c Please note that this file uses some constructs not supported by earlier 
@c versions of TeX-info.  You must be running one of the newer TeX-info 
@c releases (I currently use version 3.9 from ftp://prep.ai.mit.edu/pub/gnu/)
@c
@c Please do not send in bug reports about not being able to format the
@c document with 'makeinfo' or 'tex', just upgrade your installation.
@c
@c Info formatted files are provided in the distribution, and you can
@c retrieve dvi, postscript, and PDF versions from the web site or FTP 
@c site: http://www.cs.indiana.edu/elisp/w3/docs.html
@c
@setfilename w3.info
@settitle Emacs/W3 v4.0pre.46 User's Manual
@iftex
@c @finalout
@end iftex
@c @setchapternewpage odd
@c @smallbook
@tex
\overfullrule=0pt
%\global\baselineskip 30pt      % for printing in double space
@end tex
@synindex cp fn
@synindex vr fn
@dircategory World Wide Web
@dircategory GNU Emacs Lisp
@direntry
* Emacs/W3: (w3).                 Emacs/W3 World Wide Web browser.
@end direntry
@ifinfo
This file documents the Emacs/W3 World Wide Web browser.

Copyright (C) 1993, 1994, 1995, 1996 William M. Perry
Copyright (C) 1996, 1997 Free Software Foundation

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
are preserved on all copies.

@ignore
Permission is granted to process this file through Tex and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
@end ifinfo
@c
@titlepage
@sp 6
@center @titlefont{Emacs/W3}
@center @titlefont{User's Manual}
@sp 4
@center Third Edition, Emacs/W3 Version 4.0
@sp 1
@center June 1998
@sp 5
@center William M. Perry
@center @i{wmperry@@cs.indiana.edu}
@page
@vskip 0pt plus 1filll
Copyright @copyright{} 1993 - 1995 William M. Perry@*
Copyright @copyright{} 1996 - 1998 Free Software Foundation

Permission is granted to make and distribute verbatim copies of@*
this manual provided the copyright notice and this permission notice@*
are preserved on all copies.

@end titlepage
@page
@node Top, Getting Started, (dir), (dir)
@top W3

Users can browse the World Wide Web from within Emacs by using Emacs/W3.
All of the widely used (and even some not very widely used) @sc{url}
schemes are supported, and it is very easy to add new methods as the
need arises.

Emacs/W3 provides some core functionality that can be readily re-used
from any program in Emacs.  Users and other package writers are
encouraged to @i{Web-enable} their applications and daily work routines
with the library.

Emacs/W3 is completely customizable, both from Emacs-Lisp and from
stylesheets @xref{Stylesheets}.  If there is any aspect of Emacs/W3 that
cannot be modified to your satisfaction, please send mail to the
@t{w3-beta@@xemacs.org} mailing list with any suggestions.
@xref{Reporting Bugs}.

This manual corresponds to Emacs/W3 v4.0pre.46

@menu
* Getting Started::             Getting up and running with Emacs/W3
* Basic Usage::                 Basic movement and usage of Emacs/W3.
* Compatibility::               Explanation of compatibility with
                                other browsers.
* Display Variables::           How to control Emacs/W3's look.
* Stylesheets::                 How to control the look of web pages
* Supported URLs::              What @sc{URL} schemes are supported.
* MIME Support::                Support for @sc{mime}
* Security::                    Various security methods supported
* Cookies::                     Emacs/W3 and cookies.
* Non-Unix Operating Systems::  Special considerations necessary to get
                                up and running correctly under non-unix
                                OS's.
* Speech Integration::          Outputting to a speech synthesizer.
* Advanced Features::           Some of the more arcane features.
* More Help::                   How to get more help---mailing lists,
                                newsgroups, etc.
* Future Directions::           Plans for future revisions

Appendices:
* Reporting Bugs::              How to report a bug in Emacs/W3.
* Dealing with Firewalls::      How to get around your firewall.
* Proxy Gateways::              Using a proxy gateway with Emacs/W3.
* Installing SSL::              Turning on @sc{ssl} support.
* Mailcap Files::               An explanation of Mailcap files.
* Temporary::

Indices:
* General Index::               General Index.
* Key Index::                   Menus of command keys and their references.
@end menu

@node Getting Started, Basic Usage, Top, Top
@chapter Getting Started
@cindex Clueless in Seattle
@cindex Getting Started
@kindex M-x w3
@vindex w3-default-homepage
@findex w3
If installed correctly, starting Emacs/W3 is quite painless.  Just type
@kbd{M-x w3} in a running Emacs session.  This will retrieve the default
page that has been configured --- by default the documentation for
Emacs/W3 at Indiana University.  The default homepage is specified by
the @code{w3-default-homepage} variable.

If the default page is not retrieved correctly at startup, you will have
to do some customization.

Once started, you can use the mouse and the menu or use the following
key commands (for more commands and more detail, @pxref{Basic Usage, ,
Basic Usage}).

@table @asis
@item move forward 
press the space bar, 

@item move backwards
press the backspace key, 

@item move to the next HTML reference on the page
press the @kbd{TAB} key,

@item move to the previous HTML reference on the page
press the @kbd{SHIFT} and @kbd{TAB} keys at the same time.  If this does
not work (some text terminals cannot distinguish between @kbd{TAB} and
@kbd{SHIFT-TAB}, pressing the @kbd{ALT} and @kbd{TAB} keys should also
work.

@item follow a link 
put the cursor over it
and press the @kbd{RETURN} key, or @*
click the left mouse button on it,

@item fetch a @sc{url}
press the @kbd{Control} and @kbd{o} keys at the same time,@*
type the @sc{url}, and then press the @kbd{RETURN} key,

@item return to the last URL you were at 
press the @kbd{l} key,

@item quit W3 mode 
press the @kbd{q} key.
@end table

@menu
* Downloading::                 Where to download Emacs/W3.
* Building and Installing::     Compiling and installing from source.
* Startup Files::               What is where, and why.
@end menu

@node Downloading, Building and Installing, Getting Started, Getting Started
@section Downloading

Emacs/W3 will work with Emacs 19.29 and later and XEmacs 19.14 and later,
but if you're using a 19.x Emacs then you will need to get the
latest custom and widget libraries.

@table @asis
@item Emacs
Available from the GNU archive @uref{ftp://prep.ai.mit.edu/pub/gnu} or
one of it's many mirrors.

@item XEmacs
Available from the XEmacs archive @uref{http://www.xemacs.org/} or one
of it's many mirrors.

@item Emacs/W3
@uref{http://www.cs.indiana.edu/elisp/w3/docs.html} is the main
distribution point for Emacs/W3.

@item Emacspeak
A speech synthesizer package for Emacs and XEmacs.  More information is
available at
@uref{http://www.cs.cornell.edu/Info/People/raman/emacspeak/}

@end table

@node Building and Installing, Startup Files, Downloading, Getting Started
@section Building and Installing

Emacs/W3 uses GNU @samp{configure} (@pxref{Top, , ,configure}) to
control installation.  configure will attempt to find what version of
Emacs you have and where it is installed.  If it finds both Emacs and
XEmacs, then XEmacs is used (but see below for how to change this).
Apart from the usual options, the following options are accepted:

@table @samp
@item --with-xemacs
Use XEmacs.
@item --with-emacs
Use Emacs.
@item --with-lispdir=@var{dir}
Put lisp files (*.el and *.elc) in @var{dir}.  If this is not specified,
and neither is @samp{--with-package-dir}, then the lisp files go into
@file{@var{EMACS}/site-lisp}.
@item --with-package-dir=@var{dir}
If using XEmacs, install Emacs/W3 as a package in @var{dir}.  Please
note that this and the @samp{--prefix} argument are mutually exclusive.
@item --with-makeinfo=@var{makeinfo}
Use @var{makeinfo} to build info files from Texinfo files.
@samp{configure} will normally find makeinfo if it's available, you
should only need to specify this if it's not called makeinfo or if it
isn't in a directory in your @samp{PATH}.
@item --with-custom=@var{dir}
Use the custom package in @var{dir}.  @samp{configure} will attempt to
find a suitable custom package, you should not need to specify this
yourself if the custom package is in Emacs's @code{load-path}.
@item --enable-site-install
Install Emacs/W3 for the site, rather than just yourself.  This only
affects whether @samp{make dotemacs} affects @file{~/.emacs} or
@file{site-lisp/default.el}.

@end table

These are the most useful of the normal @samp{configure} options.

@table @samp
@item --prefix=@var{dir}
This is the top level directory and by default everything is installed
somewhere below this.  This is @file{/usr/local} by default.
@item --infodir=@var{dir}
Where to put the info files.  This is @file{@var{prefix}/info} by
default.
@item --data-dir=@var{dir}
Where to put date files (default stylesheets).  This is @file{@var{prefix}/share} by
default unless @samp{--with-package-dir=@var{pack-dir}} was given in
which case they go into @file{@var{pack-dir}/etc/w3}.
@end table

The directory that the byte-compiled lisp files will be installed into
is controlled by the @samp{--prefix}, @samp{--with-package-dir} and
@samp{--with-lispdir} options.  The directory for the info and data files is
likewise controlled by the @samp{--prefix}, @samp{--with-package-dir}
and @samp{--infodir} or @samp{--data-dir} options.

Normally these are the only things that need to be installed, they can
by compiled by @samp{make all}, or @samp{make w3} and @samp{make info}.
@samp{make install} will install the lisp, info and data files.
@samp{make all} in the @file{texi} directory will create the info files
and also dvi files.  @sc{html} and postscript can be generated by @samp{make
html} and @samp{make ps} respectively.

@c gdj1: document the other targets, fast etc.?

@node Startup Files,  , Building and Installing, Getting Started
@section Startup Files
@cindex Startup files
@cindex .w3

@vindex w3-configuration-directory
Emacs/W3 needs a directory for each user to store options, history and
the cache.  @code{w3-configuration-directory} controls this directory,
which is @file{~/.w3} by default.

@subsection Emacs/W3 profile
@cindex profile
@vindex w3-default-configuration-file
Emacs/W3 keeps a file called @file{profile} in your configuration
directory that sets many variables.  @strong{Warning}: this file will
overide any options that you set in your @file{.emacs}.  You @emph{must} either
edit @file{profile} directly or use @code{w3-menu-save-options} to save
your settings.

If you prefer, you can set @code{w3-default-configuration-file} to
specify a different configuration file.  This file does not need to be
dedicated to Emacs/W3 because Emacs/W3 will delimit its part of the file
so you can set this to @file{.emacs} if you want.  However, while
Emacs/W3 will save it's options to the correct part of the file, it will
read (and execute) the entire file when starting.

@subsection Default stylesheets
@cindex Default stylesheet
@vindex w3-default-stylesheet
Emacs/W3 will look for style-sheets in @code{w3-configuration-directory}
as well as the site-wide directories.  In particular it will look for
@file{dark.css} or @file{stylesheet-dark} if you're using a dark
background and @file{light.css} or @file{stylesheet-light} if you're
using a light background as well as @file{stylesheet} and
@file{default.css}.  If @code{w3-default-stylesheet} is not @code{nil}
then the file that it names will be used as well.  For more information,
@xref{Stylesheets}.

@subsection History
@cindex history
@vindex url-global-history-file
@vindex url-global-history-save-interval
@vindex url-keep-history
Emacs/W3 keeps a file called @file{history} in the configuration
directory.  This is a list of all the links you have visited.  You can
change the file where the history is stored by setting
@code{url-global-history-file} to the name of the file you'd prefer.
@xref{Global History}.

@subsection Hotlists
@vindex w3-hotlist-file
@dfn{Hotlists} (sometimes called bookmarks, but not to be confused with
Emacs's bookmarks) are a list of @sc{url}s.  Emacs/W3 supports mosaic's
hotlist format which associates an alias with each @sc{url} ---
@xref{Hotlist Handling}.
@c gdj1:
@c --- and also the @sc{html} style hotlists used by
@c lynx and netscape.
@c And others?
The @code{w3-hotlist-file} variable specifies
the hotlist file.  It defaults to @file{.mosaic-hotlist-default}.

@node Basic Usage, Compatibility, Getting Started, Top
@chapter Basic Usage
@cindex Basic Usage
@kindex space
@kindex backspace
@kindex return
@kindex tab
@kindex M-tab
Emacs/W3 is similar to the Info package all Emacs users hold near and
dear to their hearts (@xref{Top,,Info,info, The Info Manual}, for a
description of Info).  Basically, @kbd{space} and @kbd{backspace}
control scrolling, and @kbd{return} or the middle mouse button follows a
hypertext link.  The @kbd{tab} and @kbd{Meta-tab} keys maneuver around the
various links on the page.

@b{NOTE:} Starting with Emacs/W3 4.0, form entry areas in a page can be
typed directly into.  This is one of the main differences in navigation
from version 2.0.  If you are used to using the @kbd{f} and @kbd{b} keys
to navigate around a buffer, I suggest training yourself to always use
@kbd{tab} and @kbd{M-tab} --- it will save time and frustration on pages
with lots of form fields.

By default, hypertext links are surrounded by '[[' and ']]' on
non-graphic terminals (VT100, DOS window, etc.).  On a graphics
terminal, the links are in shown in different colors.
For information on how to change this, @xref{Stylesheets}.


There are approximately 50 keys bound to special Emacs/W3 functions.
The basic rule of thumb regarding keybindings in Emacs/W3 is that a
lowercase key takes an action on the @b{current document}, and an
uppercase key takes an action on the document pointed to by the
hypertext link @b{under the cursor}.

There are several areas that the keybindings fall into: movement,
information, action, and miscellaneous.

@menu
* Movement::                    Moving around in the buffer.
* Information::                 Getting information about a document.
* Action::                      Following links, printing, etc.
* Miscellaneous::               Everything else.
@end menu

@node Movement, Information, Basic Usage, Basic Usage
@section Movement

All the standard Emacs bindings for movement are still in effect, with a
few additions for convenience.

@table @kbd
@findex w3-scroll-up
@kindex space
@item space
Scroll downward in the buffer.  With prefix arg, scroll down that many
screenfuls (@code{w3-scroll-up}).
@item M-space
@kindex M-space
@findex w3-next-document
Goes to next document.
@c gdj1: check

@item M-del
@kindex M-del
@findex w3-prev-document
Goes to previous document.
@c gdj1: check

@kindex backspace
@kindex C-?
@findex scroll-down
@item backspace, C-?
Scroll upward in the buffer.  With prefix arg, scroll up that many
screenfuls (@code{scroll-down}).
@kindex <
@findex w3-start-of-document
@item <
Goes to the start of document (@code{w3-start-of-document}).
@kindex >
@findex w3-end-of-document
@item >
Goes to the end of document (@code{w3-end-of-document}).
@kindex b
@kindex Meta-tab
@findex w3-widget-backward
@item Meta-tab, Shift-tab, b
Attempts to move backward one link area in the current document
(@code{w3-widget-backward}).  Signals an error if no previous links are
found.
@kindex f
@kindex tab
@kindex n
@findex w3-widget-forward
@item tab, f, n
Attempts to move forward one link area in the current document
(@code{w3-widget-forward}).  Signals an error if no more links are
found.
@kindex B
@kindex HB
@findex w3-backward-in-history
@findex w3-history-backward
@item B, HB
Takes one step back along the path in the current history
(@code{w3-history-backward}).  Has no effect if at the beginning of the
session history.
@kindex F
@kindex H F
@findex w3-forward-in-history
@findex w3-history-forward
@item F, HF
Takes one step forward along the path in the current history
(@code{w3-history-forward}).  Has no effect if at the end of the session
history.
@kindex l
@findex w3-goto-last-buffer
@item l
Return to the last buffer shown before this buffer
(@code{w3-goto-last-buffer}).
@kindex q
@findex w3-quit
@item q
Kill this buffer (@code{w3-quit}).
@kindex Q, u
@findex w3-leave-buffer
@item Q, u
Bury this buffer, but don't kill it (@code{w3-leave-buffer}).
@end table

@node Information, Action, Movement, Basic Usage
@section Information

These functions relate information about one or more links on the
current document.

@table @kbd
@kindex v
@findex url-view-url
@item v
This shows the @sc{url} of the current document in the minibuffer
(@code{url-view-url}).
@kindex V
@findex w3-view-this-url
@item V
This shows the @sc{url} of the hypertext link under point in the
minibuffer (@code{w3-view-this-url}).
@kindex i
@findex w3-document-information
@item i
Shows miscellaneous information about the currently displayed document
(@code{w3-document-information}).  This includes the @sc{url}, the last
modified date, @sc{mime} headers, the @sc{http} response code, and any
relationships to other documents.  Any security information is also
displayed.
@kindex I
@findex w3-popup-info
@item I
Shows information about the @sc{url} at point (@code{w3-popup-info}).
@kindex s
@findex w3-source-document
@item s
This shows the @sc{html} source of the current document in a separate
buffer (@code{w3-source-document}).  The buffer's name is based on the
document's @sc{url}.
@kindex S
@findex w3-source-document-at-point
@item S
Shows the @sc{html} source of the hypertext link under point in a
separate buffer (@code{w3-source-document-at-point}).  The buffer's name
is based on the document's @sc{url}.
@kindex k
@findex w3-save-url
@item k
This stores the current document's @sc{url} in the kill ring, and also in the
current window-system's clipboard, if possible (@code{w3-save-url}).
@kindex K
@findex w3-save-this-url
@item K
Stores the @sc{url} of the document under point in the kill ring, and also in
the current window-system's clipboard, if possible (@code{w3-save-this-url}).
@end table

@node Action, Miscellaneous, Information, Basic Usage
@section Action

First, here are the keys and functions that bring up a new hypertext
page, usually creating a new buffer.
@table @kbd
@kindex m
@findex w3-complete-link
@item m
Choose a link from the current buffer and follow it
(@code{w3-complete-link}).  A completing-read is done on all the links,
so @kbd{space} and @kbd{TAB} can be used for completion.
@kindex return
@findex w3-follow-link
@item return 
Pressing return when over a hyperlink attempts to follow the link
under the cursor (@code{w3-follow-link}).

Pressing return when over a form input field can cause auto-submission
of the form.  This is for Mosaic and Netscape compatibility.  If there
is only one item in the form other than submit or reset buttons, then
the form will be submitted.

@kindex Middle Mouse Button
@findex w3-follow-mouse
@item Middle Mouse Button
Attempt to follow a hypertext link under the mouse cursor
(@code{w3-follow-mouse}).  Clicking on a form input field will prompt in
the minibuffer for the data to insert into the input field.  Type
checking is done, and the data is only entered into the form when data
of the correct type is entered (ie: cannot enter 44 for 'date' field,
etc).

@kindex Control Middle Mouse Button
@kindex Meta return
@findex w3-follow-inlined-image
@item Control Middle Mouse Button, Meta return
Tries to retrieve the inlined image that is under point
(@code{w3-follow-inlined-image}).  It ignores any form entry areas or
hyperlinks, and blindly follows any inlined image.  Useful for seeing
images that are meant to be used as hyperlinks when not on a terminal
capable of displaying graphics.

@kindex D
@findex w3-download-url-at-point
@item D
Download the @sc{url} at point (@code{w3-download-url-at-point}).
@kindex d
@findex w3-download-this-url
@item d
Download the current @sc{url} (@code{w3-download-this-url}).
@c @kindex G
@c @findex w3-show-graphics
@c @c @item G
@c gdj1: Bound to w3-show-graphics which isn't defined.
@c @kindex p
@kindex m
@findex w3-complete-link
@item m
Selects a destination from a list of all the hyperlinks in the current
buffer (@code{w3-complete-link}).  Use @kbd{space} and @kbd{tab} to
complete on the links.

@kindex r
@kindex g
@findex w3-reload-document
@item r, g
Reloads the current document (@code{w3-reload-document}).  The position
within the buffer remains the same (unless the document has changed
since it was last retrieved, in which case it should be relatively
close).  This causes an unconditional reload from the remote server ---
the locally cached copy is not consulted.
@kindex R
@findex w3-refresh-buffer
@item R
Redraws the buffer without reloading document (@code{w3-refresh-buffer}).
@kindex C-o
@findex w3-fetch
@item C-o
Prompts for a @sc{url} in the minibuffer, and attempts to fetch it
(@code{w3-fetch}).  If there are any errors, or Emacs/W3 cannot
understand the type of link requested, the errors are displayed in a
hypertext buffer.
@kindex o
@findex w3-open-local
@vindex url-use-hypertext-dired
@item o
Opens a local file, interactively (@code{w3-open-local}).  This prompts
for a local file name to open.  The file must exist, and may be a
directory.  If the requested file is a directory and
@code{url-use-hypertext-dired} is @code{nil}, then a dired-mode buffer
is displayed.  If non@code{nil}, then Emacs/W3 automatically generates a
hypertext listing of the directory.  The hypertext mode is the default,
so that all the keys and functions remain the same.

@kindex M-s
@findex w3-save-as
@item M-s
Save a document to the local disk as HTML Source, Formatted Text, LaTeX
Source, or Binary (@code{w3-save-as}).

@kindex Hv
@kindex C-c C-b
@findex w3-show-history-list
@item Hv, C-c C-b
Show the current session's history list (@code{w3-show-history-list}).
This takes all the links that are in that internal list, and formats
them as hypertext links in a list, @ref{Global History}
@end table

@cindex Buffer movement
And here are the commands to move around between Emacs/W3 buffers:

@table @kbd
@kindex l
@findex w3-goto-last-buffer
@item l
Goes to the last WWW buffer seen (@code{w3-goto-last-buffer}).
@kindex p
@findex w3-print-this-url
@item p
Prints the current document (@code{w3-print-this-url}).  Choose from several different formats to
print: formatted text, @sc{html} source, PostScript (with ps-print), or by using
LaTeX and dvips).  @ref{Printing}.
@kindex P
@findex w3-print-url-under-point
@item P
Prints out the @sc{url} under point in a variety of formats
(@code{w3-print-url-under-point}).  @ref{Printing}.
@kindex q
@findex w3-quit
@item q
Quits WWW mode (@code{w3-quit}).  This kills the current buffer and goes
to the most recently visited buffer.
@kindex Q
@kindex u
@findex w3-leave-buffer
@item u, Q
This (@code{w3-leave-buffer}) is similar to @code{w3-quit}, but the
buffer is not killed, it is moved to the bottom of the buffer list (so
it is the least likely to show up as the default with switch-to-buffer).
This is different from @code{w3-goto-last-buffer} in that it does not
return to the last @sc{WWW} page visited --- it is the same as using
@code{switch-to-buffer} --- the buffer left in the window is fairly
random.
@end table

@node Miscellaneous,  , Action, Basic Usage
@section Miscellaneous

@table @kbd
@kindex ?
@findex w3-help
@item ?
Shows help for Emacs/W3 (@code{w3-help}).
@kindex C-c C-v
@findex w3-version
@item C-c C-v
Show what version of Emacs/W3 you're running (@code{w3-version}).
@kindex M-m
@findex w3-mail-current-document
@item M-m
Mails the current document to someone (@code{w3-mail-current-document}).
Choose from several different formats to mail: formatted text, @sc{html}
source, PostScript, or LaTeX source.  When the @sc{html} source is
mailed, then an appropriate <base> tag is inserted at the beginning of
the document so that relative links may be followed correctly by whoever
receives the mail.
@kindex M-M
@findex w3-mail-document-under-point
@item M-M
Mails the document pointed to by the hypertext link under point to
someone (@code{w3-mail-document-under-point}).  Choose from several
different formats to mail: formatted text, @sc{html} source, PostScript,
or LaTeX source.  When the @sc{html} source is mailed, then an
appropriate <base> tag is inserted at the beginning of the document so
that relative links may be followed correctly by whoever receives the
mail.
@kindex A-t
@kindex M-t
@findex url-list-processes
@item M-t, A-t
gdj1: bound to url-list-processes.  What does this do?
@kindex c
@findex w3-mail-document-author
@item c
Send a mail to the author of the current document
(@code{w3-mail-document-author}).

@kindex M-x w3-insert-formatted-url
@findex w3-insert-formatted-url
@item M-x w3-insert-formatted-url
Insert a fully formatted @sc{html} link into another buffer
(@code{w3-insert-formatted-url}).  This gets the name and @sc{url} of
either the current buffer, or, with a prefix arg, of the link under
point, and construct the appropriate <a...>...</a> markup and insert it
into the desired buffer.
@kindex M-tab
@findex w3-insert-this-url
@item M-tab
Inserts the @sc{url} of the current document into another buffer
(@code{w3-insert-this-url'}).  Buffer is prompted for in the minibuffer.
With prefix arg, uses the @sc{url} of the link under point.
@kindex U
@findex w3-use-links
@item U
Selects one of the <LINK> tags from this document and fetch it
(@code{w3-use-links}).  Links are attributes of a specific document, and
can tell such things as who made the document, where a table of contents
is located, etc.

Link tags specify relationships between documents in two ways.  Normal
(forward) relationships (where the link has a REL="xxx" attribute), and
reverse relationships (where the link has a REV="xxx" attribute).  This
first asks what type of link to follow (Normal or Reverse), then does
a @code{completing-read} on only the links that have that type of
relationship.
@end table

@node Compatibility, Display Variables, Basic Usage, Top
@chapter Compatibility with other Browsers
Due to the popularity of several other browsers, Emacs/W3 offers an easy
transition to its much better way of life.  This ranges from being able
to share the same preferences files and disk cache to actually emulating
the keybindings used in other browsers.

@menu
* Emulation::                   Emacs/W3 can emulate the keybindings and
				other behaviours of other browsers.
* Hotlist Handling::            A hotlist is an easy way to keep track of
				interesting Web pages without having to
				remember the exact path to get there.
* Session History::             Keeping a history of documents visited
				in one Emacs sessions allows the use of
				'forward' and 'back' buttons easily.
* Global History::              Keeping a history of all the places ever
				visited on the web.
@end menu

@node Emulation, Hotlist Handling, Compatibility, Compatibility
@section Emulation

@cindex Browser emulation
@cindex Emulation of other browsers
@vindex w3-mode-hook
Emacs/W3 can emulate the keybindings of lynx and netscape, but only one
at a time.  If you want emulation permanantly turned on, then you should
add @code{turn-on-lynx-emulation} or @code{turn-on-netscape-emulation}
to @code{w3-mode-hook}.

@menu
* lynx::                        Emulate lynx.
* netscape::                    Emulate netscape.
* Masquerading::                Emacs/W3 can masquerade as another
                                browser.
@end menu

@node lynx, netscape, Emulation, Emulation
@section Lynx emulation
@cindex Lynx emulation
@findex turn-on-lynx-emulation
@findex w3-lynx-emulation-minor-mode

@code{turn-on-lynx-emulation} turns on lynx emulation and turns off
netscape emulation.  lynx emulation is handled by the
@code{w3-lynx-emulation-minor-mode} minor mode.  For more information
about lynx style hotlists, @xref{Hotlist Handling}.


:: work :: Document lynx emulation@*
@table @kbd
@kindex down
@item Down arrow
Highlight next topic
@kindex up
@item Up arrow
Highlight previous topic
@kindex right
@kindex return
@item Right arrow, Return, Enter
Jump to highlighted topic
@kindex left
@item Left arrow
Return to previous topic.  gdj1: actually, this doesn't seem to work
quite right.
@kindex +
@item +
Scroll down to next page (Page-Down)
@kindex -
@item -
Scroll up to previous page (Page-Up)
@kindex space
@item SPACE
Scroll down to next page (Page-Down)
@kindex b
@item b
Scroll up to previous page (Page-Up)
@kindex C-a
@item C-a
Go to first page of the current document (Home)
@kindex C-b
@item C-e
Go to last page of the current document (End)
@kindex C-b
@item C-b
Scroll up to previous page (Page-Up)
@kindex C-f
@item C-f
Scroll down to next page (Page-Down)
@kindex C-n
@item C-n
Go forward two lines in the current document
@kindex C-p
@item C-p
Go back two lines in the current document
@kindex )
@item )
Go forward half a page in the current document (ignored)
@kindex (
@item (
Go back half a page in the current document (ignored)
@kindex #
@item #
Go to Toolbar or Banner in the current document, only works in XEmacs.
gdj1: is this what is meant by toolbar?
@kindex ?
@kindex h
@item ?, h
Help (this screen)
@kindex a
@item a
Add the current link to a bookmark file
@kindex c
@item c
Send a comment to the document owner 
@kindex d
@item d
Download the current link
@kindex e
@item e
Edit the current file (ignored)
@kindex g
@item g
Goto a user specified @sc{url} or file
@kindex i
@item i
Show an index of documents (ignored)
@kindex j
@item j
Execute a jump operation (using hotlist)
@kindex k
@item k
Show a list of key mappings
@kindex l
@item l
List references (links) in current document
@kindex m
@item m
Return to main screen
@kindex n
@item n
Go to the next search string
@kindex o
@item o
Set your options
@kindex p
@item p
Print the current document
@kindex q
@item q
Quit
@kindex r
@item r
Delete hotlist entry
@kindex s
@item s
Enter a search string for an external search gdj1: really?
@kindex u
@item u
Go backwards in history
@kindex /
@item /
Search for a string within the current document
@kindex v
@item v
View a bookmark file
@kindex V
@item V
Go to the Visited Links Page
@kindex x
@item x
Force submission of form or link with no-cache
@kindex z
@item z
Cancel transfer in progress
@kindex backspace
@item [backspace]
Go to the history Page gdj1: really?
@kindex =
@item =
Show file and link info
@kindex \
@item \
Toggle document source/rendered view
@kindex !
@item !
Spawn your default shell
@kindex *
@item *
Toggle image_links mode on and off (ignored)
@kindex [
@item [
Toggle pseudo_inlines mode on and off (ignorged)
@kindex ]
@item ]
Send an @sc{http} @sc{head} request for the current doc or link (ignored)
@kindex C-r
@item C-r
Reload current file and refresh the screen
@kindex C-w
@item C-w
Refresh the screen
@kindex C-u
@item C-u
Erase input line (ignored)
@kindex C-g
@item C-g
Cancel input or transfer
@kindex C-t
@item C-t
Toggle trace mode on and off (ignored)
@kindex C-k
@item C-k
Invoke the Cookie Jar Page (ignored)
@end table

@node netscape, Masquerading, lynx, Emulation
@section Netscape emulation
@cindex Netscape emulation
@findex turn-on-netscape-emulation
@findex w3-netscape-emulation-minor-mode

@code{turn-on-netscape-emulation} turns on netscape emulation and turns
off lynx emulation.  netscape emulation is handled by the
@code{w3-netscape-emulation-minor-mode} minor mode.  For more
information about netscape style hotlists, @xref{Hotlist Handling}.



@table @kbd
@kindex M-a
@item M-a
Add the current link to a bookmark file

@kindex M-b
@item M-b
Show hotlist file.

@kindex M-f
@item M-f
Search forward in document

@kindex M-g
@item M-g
Reapeat last search

@kindex M-h
@item M-h
Show history window

@kindex M-i
@item M-i
Load images

@kindex M-l
@item M-l
Goto a user specified @sc{url} or file

@kindex M-m
@item M-m
Send mail

@kindex M-n
@item M-n
Open new frame

@kindex M-o
@item M-o
Open a local file

@kindex M-p
@item M-p
Print current document

@kindex M-q
@item M-q
Quit current document

@kindex M-r
@item M-r
Reload document and redraw

@kindex M-s
@item M-s
Save current document

@kindex M-left
@item M-[left]
Go back in history list

@kindex M-right
@item M-[right]
Go forward in history list

@kindex left
@item [left]
Scroll left

@kindex right
@item [right]
Scroll right

@kindex up
@item [up]
Scroll up

@kindex down
@item [down]
Scroll down
@end table

@node Masquerading, , netscape, Emulation
@section Masquerading
@cindex Browser masquerading
@cindex Masquerading as other browsers
@findex turn-on-lynx-masquerade-mode
@findex turn-on-netscape-masquerade-mode
@findex turn-on-ie-masquerade-mode
@findex turn-on-arena-masquerade-mode
@findex turn-off-lynx-masquerade-mode
@findex turn-off-netscape-masquerade-mode
@findex turn-off-ie-masquerade-mode
@findex turn-off-arena-masquerade-mode
@findex w3-arena-masquerade-mode
@findex w3-ie-masquerade-mode
@findex w3-netscape-masquerade-mode
@findex w3-lynx-masquerade-mode
@sc{http} allows servers to ask browsers what browser they are, and what
version they are.  Emacs/W3 allows you to choose the reply.  There are
functions to masquerade as lynx, netscape, @sc{ie} or arena.  For each
@var{browser} there are three functions,
@code{turn-on-@var{browser}-masquerade-mode},
@code{turn-off-@var{browser}-masquerade-mode} and
@code{w3-@var{browser}-masquerade-mode}.  The purpose of the first two
is clear, @code{w3-@var{browser}-masquerade-mode} takes an optional
argument which toggles the mode if it's @code{nil}, turns off the mode
if it's 0 and turns the mode on otherwise.

If you'd prefer to masquerade as another browser, then you should call
@code{w3-masquerade-stub} with three arguments: @var{arg}, @var{app} and
@var{version}.  @var{arg} has the same function as for
@code{w3-@var{browser}-masquerade-mode}, @var{app} is the name of the
browser to masquerade as and @var{version} is the version.

Why would you want to masquerade as another browser when you could be
advertising Emacs/W3?  Well, some servers will only let certain browsers
connect with them.  This is cleary evil.  Also some servers may alter
what they present depending on the browser, this is probably a Good
Thing but they might not know about Emacs/W3.  Also one could argue that
demanding the USER_AGENT field is a breach of privacy, Emacs/W3 doesn't
have to send it (@pxref{Security}), but the server doesn't have
to let you connect either.


@node Hotlist Handling, Session History, Emulation, Compatibility
@section Hotlist Handling

Emacs/W3 supports two types of hotlist, mosaic hotlists and @sc{html} as
used by lynx and netscape (which both call hotlists bookmarks).
Unfortunately, not all hotlist operations are supported for @sc{html}
files at the moment.

In order to avoid having to traverse many documents to get to the same
document over and over, Emacs/W3 supports a ``hotlist'' like Mosaic.  This is
a file that contains @sc{url}s and aliases.  Hotlists allow quick access to any
document in the Web, providing it has been visited and added to the hotlist.
The variable @code{w3-hotlist-file} determines where this information
is saved.  The structure of the file is compatible with Mosaic's
hotlist file, so this defaults to @file{~/.mosaic-hotlist-default}.

Hotlist commands are:
@table @kbd
@item ha
@kindex ha
@findex w3-hotlist-apropos
Shows the hotlist entries matching a regular expression.

@kindex hi
@findex w3-hotlist-add-document
@vindex w3-hotlist-file
@item hi
Adds the current document to the hotlist, with the buffer name as its
identifier.  Modifies the file specified by @code{w3-hotlist-file}.  If
this is given a prefix-argument (via @kbd{C-u}), the title is prompted
for instead of automatically defaulting to the document title.

@findex w3-hotlist-delete
@vindex w3-hotlist-file
@kindex hd
@item hd
Prompts for the alias of the entry to kill.  Pressing the spacebar or
tab will list out partial completions.  The internal representation of
the hotlist and the file specified by @code{w3-hotlist-file} are
updated. 

@item hr
@kindex hr
@findex w3-hotlist-rename-entry
@vindex w3-hotlist-file
Some hotlist item names can be very unwieldy (`Mosaic for X level 2 fill
out form support'), or uninformative (`Index of /').  Prompts for the
item to rename in the minibuffer---use the spacebar or tab key for
completion.  After having chosen an item to rename, prompts for a new
title until a unique title is entered.  Modifies the file specified by
@code{w3-hotlist-file}.

@item hu
@kindex hu
@findex w3-use-hotlist
Prompts for the alias to jump to.  Pressing the @key{spacebar} or
@key{tab} key shows partial completions.

@item hv
@kindex hv
@findex w3-show-hotlist
Converts the hotlist into @sc{html} and displays it.

@item hA
@kindex hA
@findex w3-hotlist-append
Appends another hotlist file to the one currently in memory.

@item hI
@kindex hI
@findex w3-hotlist-add-document-at-point
Add the document pointed to by the hyperlink under point to the hotlist.

@findex w3-hotlist-refresh
@vindex w3-hotlist-file
@kindex hR
@item hR
This rereads the default hostlist file specified by
@code{w3-hotlist-file}.

@end table


@node Session History, Global History, Hotlist Handling, Compatibility
@section History
@cindex History Lists

Almost all web browsers keep track of the @sc{url}s followed from a page, so
that it can provide @b{forward} and @b{back} buttons to keep a @i{path}
of @sc{url}s that can be traversed easily.

@vindex url-keep-history
If @code{url-keep-history} is non-@code{nil}, then Emacs/W3 keeps track
of all the @sc{url}s visited in an Emacs session.  If @code{t} then
Emacs/W3 will save the history list at the end of each session to the
@code{url-global-history-file} file.  The history list is simply a list
of all the @sc{url}s visited in the session.

@findex w3-show-history-list
To view a listing of the history for this session of Emacs/W3, use
@code{M-x w3-show-history-list} (@kbd{Hv}) from any buffer, and Emacs/W3
generates an @sc{html} document showing every @sc{url} visited since
Emacs started (or cleared the history list), and then format it.  Any of
the links can be chosen and followed to the original document.  To clear
the history list, choose 'Clear History' from the 'Options' menu.

@findex w3-forward-in-history
@findex w3-backward-in-history
@findex w3-fetch
Another twist on the history list mechanism is the fact that all
Emacs/W3 buffers remember what @sc{url}, buffer, and buffer position of the
last document, and also keeps track of the next location jumped @b{to}
from that buffer.  This means that the user can go forwards and
backwards very easily along the path taken to reach a particular
document.  To go forward, use the function @code{w3-forward-in-history} (@kbd{F}),
to go backward, use the function @code{w3-backward-in-history}
(@kbd{B}).  To view the entire history, use @code{w3-show-history-list}
(@kbd{Hv}).


@node Global History,  , Session History, Compatibility
@section Global History

Most web browsers also support the idea of a ``history'' of @sc{url}s
the user has visited, and it displays them in a different style than
normal @sc{url}s.  Emacs/W3 will read and write history files generated
by Emacs/W3, Mosaic v1 and v2 or netscape.  Emacs/W3 looks at the file
contents to determine the type of history.

@vindex url-keep-history
@vindex url-global-history-file
@vindex url-global-history-save-interval
If the variable @code{url-keep-history} is @code{t}, then Emacs/W3 keeps
a list of all the @sc{url}s visited in a session.  The file is
automatically written to disk every
@code{url-global-history-save-interval} seconds and when exiting emacs.
The list is added to those already in the file specified by
@code{url-global-history-file}, which defaults to @file{~/mosaic.hst}
for MS operating systems, @file{~/mosaic.global-history} for @sc{VMS} and
@file{~/.w3/history} for everything else.

If any @sc{url} in the list is found in the file, it is not saved, but new
ones are added at the end of the file.

The function that saves the global history list is smart enough to
notice what style of history list is being used (Netscape, Emacs/W3, or
XMosaic), and writes out the new additions appropriately.

@cindex Completion of URLs
@cindex Usefulness of global history
One of the nice things about keeping a global history files is that Emacs/W3
can use it as a completion table.  When doing @kbd{M-x w3-fetch}, pressing
the @kbd{tab} or @kbd{space} key will show all completions for a
partial @sc{url}.  This is very useful, especially for very long @sc{url}s that
are not in a hotlist, or for seeing all the pages from a particular web
site before choosing which to retrieve.

@node Display Variables, Stylesheets, Compatibility, Top
@section Display Variables

Emacs/W3 has many variable for you to fiddle with to get the display
just right.

@table @code
@item w3-display-frames
@vindex w3-display-frames
You can control what Emacs/W3 does with frame by setting
@code{w3-display-frames}.  It can be
@table @code
@item nil
Emacs/W3 will pretend not to understand frames at all.
@item as-nil
Emacs/W3 will show hyperlinks to frames but will not fetch them (the same
behaviour as lynx).
@item ask
This is similar to @code{as-nil}, but Emacs/W3 will ask if you want to
retrieve the frames.
@item t
Emacs/W3 will display the hyperlinks and fetch the frames.
@end table

@item w3-bullets
@vindex w3-bullets
Emacs/W3 lets @emph{you} decide what characters to use for bullets in
unordered lists by setting @code{w3-bullets}.  It is a association list,
mapping list types to characters.  By default it is @code{((disc . ?*)
(circle . ?o) (square . ?#) (none . ? ))}.

@item w3-echo-link
@vindex w3-echo-link
You can decide what should be displayed when tabbing through links by
setting the @code{w3-echo-link} variable.  It is a list and may contain
the following symbols,
@table @code
@item url
Display the @sc{url} of the target.
@item text
Display the text of the link.
@item title
Display the title attribute of the link.
@item name
Display the name or id attribute of the link.
@end table

The default is @code{(title url text name)}.

@item w3-horizontal-rule-char
@vindex w3-horizontal-rule-char
Many @sc{html} pages use horizontal lines (rules) to separate sections
of the page.  You can control what character Emacs/W3 will use to draw
these by setting @code{w3-horizontal-rule-char}.  If it is a character
(@emph{not} a string) then Emacs/W3 will replicate that character across
the screen, if it is @code{nil} then Emacs/W3 will use a terminal
graphics character if possible.  It is @code{nil by default}.

@item w3-use-terminal-characters
@vindex w3-use-terminal-characters
When Emacs/W3 draws table and rules, it needs to approximate line
somehow.  If @code{w3-use-terminal-characters} it @code{non-nil} (the
default) then Emacs/W3 will use terminal graphics characters if they are
available.

@item w3-use-terminal-characters-on-tty
@vindex w3-use-terminal-characters-on-tty
Using terminal graphics characters on ttys will trigger display bugs in
both XEmacs and FSF Emacs, but the display is usually readable with FSF
Emacs.  @code{w3-use-terminal-characters-on-tty} controls whether to use
terminal graphics characters on ttys, it is @code{nil} by default.

@item w3-use-terminal-glyphs
@vindex w3-use-terminal-glyphs
Emacs/W3 can use glyphs rather than text properties for terminal
graphics characters.  Glyphs do not work with the most recent versions
of XEmacs.  This is @code{t} by default.

@item w3-defined-link-types
@vindex w3-defined-link-types
@code{w3-defined-link-types} is a list of names that have special
significance as the values of @samp{REL} or @samp{REV} attributes of
<link> elements.  All members should be in lowercase.

@item w3-auto-image-alt
@vindex w3-auto-image-alt
Some people do not feel it's worth their time to add @code{alt} tags to
their images, but Emacs/W3 can create @code{alt} tags on the fly for
images that do not have them.  To control this you can set
@code{w3-auto-image-alt} to one of the following:
@table @asis
@item @code{nil}
Do not create @code{alt} tags
@item string
The string will be run through format with the filename of the image and
so may have a single @code{%s}, for example @code{"[IMAGE(%s)]"} 
@item function
The function will be called with the filename of the images as the
argument.  This is the default, with @code{w3-default-image-alt-func}
being the function.
@end table

@item w3-min-img-size, w3-default-image-alt-func, w3-dummy-img-alt-repl
@vindex w3-min-img-size
@vindex w3-dummy-img-alt-repl
@findex w3-default-image-alt-func
@code{w3-default-image-alt-func} returns @code{w3-dummy-img-alt-repl}
(@samp{*} by default) if the image's height and width are both less than
@code{w3-min-img-size} pixels (15 by default) and if the filename
matches the @code{w3-dummy-img-re} regular expression.  Otherwise,
@code{w3-default-image-alt-func} returns the filename enclosed in a
@samp{[]} pair.

@item w3-icon-format
@vindex w3-icon-format
Emacs/W3 will expect the standard icons to be in the format specified by
@code{w3-icon-format}.  This is @code{gif} by default, but could be
@code{xpm}, @code{xbm} or any other format for that matter.  It is added
as a file extension to the icon name, but the variable's value must be a
symbol.  If @code{nil}, then the server decides.

@item w3-delay-image-loads
@vindex w3-delay-image-loads
You can choose whether Emacs/W3 retrieves images with the document, or
delays loading them by setting @code{w3-delay-image-loads}.  By default
this is @code{t} if you compiled XEmacs with support for gifs, jpegs,
pngs or imagick and @code{nil} otherwise.

@item w3-image-mappings
@vindex w3-image-mappings
@code{w3-image-mappings} controls the mapping of @sc{mime} types to
image types for the @samp{image} package.  Each entry is a cons cell of
a @sc{mime} type string and an image-type symbol.

@item w3-max-menu-length
@vindex w3-max-menu-length
Emacs/W3 will split menus into smaller submenus if they are longer than
@code{w3-max-menu-length}.

@item w3-max-menu-width
@vindex w3-max-menu-width
The maximum width of a pulldown menu choice.

@item w3-right-margin
@vindex w3-right-margin
Emacs/W3's right margin is controlled by @code{w3-right-margin}.  This
is subtracted from @code{(window-width)} for each Emacs/W3 buffer and
used as the fill-column.  It is 2 by default.

@item w3-maximum-line-length
@vindex w3-maximum-line-length
The maximum length of a line.  If @code{nil} (the default) then lines
can extend to the window margin.

@item w3-modeline-format
@vindex w3-modeline-format
You can specify the modeline to use in @samp{w3-mode} by setting this.

@item w3-honor-stylesheets
@vindex w3-honor-stylesheets
If this is non-@code{nil} (the default) then Emacs/W3 will let a
document specify a @sc{css} stylesheet.

@item w3-user-colors-take-precedence
@vindex w3-user-colors-take-precedence
Emacs/W3 will ignore a document's attempts to define certain colours if
@code{w3-user-colors-take-precedence} it non-@code{nil}.  The default is @code{nil}.

@item w3-user-fonts-take-precedence
@vindex w3-user-fonts-take-precedence
Emacs/W3 will ignore attempts by stylesheets or font tags to change
certain fonts if this is non-@code{nil}.

@subsection Asynchronous behaviour

@item url-be-asynchronous
@vindex url-be-asynchronous
If this is non-@code{nil} then document retrievals over @sc{http} will
be down in the background.

@item url-default-retrieval-proc
@vindex url-default-retrieval-proc
This controls what happens when an asynchronous retrievel completes.  It
is @code{url-default-callback} by default but can be any function taking
one argument.  The argument specifies the file that has been retrieved.
If there is no buffer associated with the file, then
@code{url-default-callback} just puts a message in the minibuffer saying
that the retrieval is complete, otherwise the action depends on the
buffer.

@item w3-do-incremental-display
@vindex w3-do-incremental-display
Emacs/W3 can de incremental display of pages if
@code{w3-do-incremental-display} is @code{t}.  It is @code{nil} by default.

@item w3-notify
@vindex w3-notify
You might want Emacs/W3 to notify you discreetly when it has finished
preparing a page for your reading pleasure.  You can control Emacs/W3's
behaviour in this situation by way of the @code{w3-notify} variable.  It
may take the following values:
@table @code
@item newframe
Puts the Emacs/W3 page in its own frame.
@item bully
Make the Emacs/W3 page the current buffer and only window.
@item semibully
Make the Emacs/W3 page the current buffer in the same window.  This is
the default.
@item aggressive
Make the Emacs/W3 page the current buffer in the other window.
@item friendly
Display the Emacs/W3 page in the other window, but don't make it the
current buffer.
@item polite
Don't display Emacs/W3 page, but print a message when ready and beep.
@item quiet
The same as @code{polite}, but don't beep.
@item meek
Make no indication that the page is ready, in fact any other value is
equivalent to meek.
@end table

@end table


@node Stylesheets, Supported URLs, Display Variables, Top
@chapter Stylesheets
The way in which Emacs/W3 formats a document is very customizable.  All
formatting is now controlled by a default stylesheet set by the user
with the @code{w3-default-stylesheet} variable.  Emacs/W3 currently
supports the @sc{W3C} recommendation for Cascading Style Sheets, Level 1
(commonly known as @sc{CSS1}) with a few experimental items from other
W3C proposals.  Wherever Emacs/W3 diverges from the specification, it
will be clearly documented, and will be changed once a full standard is
available.

Support for @sc{DSSSL} is progressing, but spare time is at an all-time
low.  If anyone would like to help, please contact the author.

The following sections closely parallel the @sc{CSS1} specification so
it should be very easy to look up what Emacs/W3 supports when browsing
through the @sc{CSS1} specification.  Please note that a lot of the text
in the following sections comes directly from the specification as
well.

@menu
* Terminology::                 Terms used in the rest of this chapter.
* Basic Concepts::              Why are stylesheets useful?  Getting started.
* Pseudo-Classes/Elements::     Special classes for elements.
* The Cascade::                 How stylesheets are combined.
* Properties::                  What properties you can set on elements.
* Units::                       What you can set them to.
@end menu

@node Terminology, Basic Concepts, Stylesheets, Stylesheets
@section Terminology

@table @dfn
@item attribute
HTML attribute, ie: @samp{align=center} --- align is the attribute.
@item author
The author of an HTML document.
@item block-level element
An element which has a line break before and after (e.g. 'H1' in @sc{HTML}).
@item canvas
The part of the UA's drawing surface onto which documents are rendered.
@item child element
A subelement in @sc{sgml} terminology.
@item contextual selector
A selector that matches elements based on their position in the document
structure. A contextual selector consists of several simple
selectors. E.g., the contextual selector 'H1.initial B' consists of two
simple selectors, 'H1.initial' and 'B'.
@item @sc{css}
Cascading Style Sheets.
@item declaration
A property (e.g. 'font-size') and a corresponding value (e.g. '12pt').
@item designer
The designer of a style sheet.
@item document
@sc{html} document.
@item element
@sc{html} element.
@item element type
A generic identifier in @sc{sgml} terminology.
@item fictional tag sequence
A tool for describing the behavior of pseudo-classes and pseudo-elements.
@item font size
The size for which a font is designed. Typically, the size of a font is
approximately equal to the distance from the bottom of the lowest letter
with a descender to the top of the tallest letter with an ascender and
(optionally) with a diacritical mark.
@item @sc{html} extension
Markup introduced by UA vendors, most often to support certain visual
effects. The @sc{font}, @sc{center} and @sc{blink} elements are examples
of HTML extensions, as is the @sc{bgcolor} attribute. One of the goals
of @sc{css} is to provide an alternative to @sc{html} extensions.
@item inline element
An element which does not have a line break before and after
(e.g. '@sc{strong}' in @sc{html})
@item intrinsic dimensions
The width and height as defined by the element itself, not imposed by
the surroundings. In this specification it is assumed that all replaced
elements -- and only replaced elements -- come with intrinsic
dimensions.
@item parent element
The containing element in @sc{sgml} terminology.
@item pseudo-element
Pseudo-elements are used in @sc{css} selectors to address typographical
items (e.g. the first line of an element) rather than structural
elements.
@item pseudo-class
Pseudo-classes are used in @sc{css} selectors to allow information
external to the @sc{html} source (e.g. the fact that an anchor has been
visited or not) to classify elements.
@item property
A stylistic parameter that can be influenced through @sc{css}.
@item reader
The person for whom the document is rendered.
@item replaced element
An element that the @sc{css} formatter only knows the intrinsic
dimensions of. In @sc{html}, @sc{img}, @sc{input}, @sc{textarea},
@sc{select} and @sc{object} elements can be examples of replaced
elements. E.g., the content of the @sc{img} element is often replaced by
the image that the @sc{src} attribute points to.  @sc{css1} does not
define how the intrinsic dimensions are found.
@item rule
A declaration (e.g. 'font-family: helvetica') and its selector
(e.g. @sc{'H1'}).
@item selector
A string that identifies what elements the corresponding rule applies
to. A selector can either be a simple selector (e.g. 'H1') or a
contextual selector (e.g. @sc{'h1 b'}) which consists of several simple
selectors.
@item @sc{sgml}
Standard Generalized Markup Language, of which @sc{html} is an
application.
@item simple selector
A selector that matches elements based on the element type and/or
attributes, and not the element's position in the document
structure. E.g., 'H1.initial' is a simple selector.
@item style sheet
A collection of rules.
@item @sc{ua}
User Agent, often a web browser or web client.
@item user
Synonymous with reader.
@item weight
The priority of a rule.
@end table

@node Basic Concepts, Pseudo-Classes/Elements, Terminology, Stylesheets
@section Basic Concepts

Designing simple style sheets is easy. One needs only to know a little
HTML and some basic desktop publishing terminology. E.g., to set the
text color of 'H1' elements to blue, one can say:

@example 
  H1 @{ color: blue @}
@end example

The example above is a simple CSS rule. A rule consists of two main
parts: selector ('H1') and declaration ('color: blue'). The declaration
has two parts: property ('color') and value ('blue'). While the example
above tries to influence only one of the properties needed for rendering
an HTML document, it qualifies as a style sheet on its own. Combined
with other style sheets (one fundamental feature of CSS is that style
sheets are combined) it will determine the final presentation of the
document.

The selector is the link between the HTML document and the style sheet, and
all HTML element types are possible selectors.

@node Pseudo-Classes/Elements, The Cascade, Basic Concepts, Stylesheets
@section Pseudo-Classes/Elements

In @sc{css1}, style is normally attached to an element based on its
position in the document structure. This simple model is sufficient for
a wide variety of styles, but doesn't cover some common effects. The
concept of pseudo-classes and pseudo-elements extend addressing in
@sc{css1} to allow external information to influence the formatting
process.

Pseudo-classes and pseudo-elements can be used in @sc{css} selectors,
but do not exist in the @sc{html} source. Rather, they are "inserted" by
the @sc{ua} under certain conditions to be used for addressing in style
sheets. They are referred to as "classes" and "elements" since this is a
convenient way of describing their behavior. More specifically, their
behavior is defined by a fictional tag sequence.

Pseudo-elements are used to address sub-parts of elements, while
pseudo-classes allow style sheets to differentiate between different
element types.

The only support pseudo-classes in Emacs/W3 are on the anchor tag
(<a>...</a>).

User agents commonly display newly visited anchors differently from
older ones. In @sc{css1}, this is handled through pseudo-classes on the
'A' element:

@example
  A:link @{ color: red @}       /* unvisited link */
  A:visited @{ color: blue @}   /* visited links */
  A:active @{ color: lime @}    /* active links */
@end example

All 'A' elements with an 'HREF' attribute will be put into one and only
one of these groups (i.e. target anchors are not affected). UAs may
choose to move an element from 'visited' to 'link' after a certain
time. An 'active' link is one that is currently being selected (e.g. by
a mouse button press) by the reader.

The formatting of an anchor pseudo-class is as if the class had been
inserted manually. A @sc{ua} is not required to reformat a currently
displayed document due to anchor pseudo-class transitions. E.g., a style
sheet can legally specify that the 'font-size' of an 'active' link
should be larger that a 'visited' link, but the UA is not required to
dynamically reformat the document when the reader selects the 'visited'
link.

Pseudo-class selectors do not match normal classes, and vice versa. The
style rule in the example below will therefore not have any influence:

@example
  A:link @{ color: red @}

  <A CLASS=link NAME=target5> ... </A>
@end example

In @sc{css1}, anchor pseudo-classes have no effect on elements other
than 'A'. Therefore, the element type can be omitted from the selector:

@example
  A:link @{ color: red @}
  :link @{ color: red @}
@end example

The two selectors above will select the same elements in CSS1.

Pseudo-class names are case-insensitive.

Pseudo-classes can be used in contextual selectors:

@example
  A:link IMG @{ border: solid blue @}
@end example

Also, pseudo-classes can be combined with normal classes:

@example
  A.external:visited @{ color: blue @}

  <A CLASS=external HREF="http://out.side/">external link</A>
@end example

If the link in the above example has been visited, it will be rendered
in blue. Note that normal class names precede pseudo-classes in the
selector.

@node The Cascade, Properties, Pseudo-Classes/Elements, Stylesheets
@section The Cascade

In @sc{css}, more than one style sheet can influence the presentation
simultaneously. There are two main reasons for this feature: modularity
and author/reader balance.

@table @i
@item modularity
A style sheet designer can combine several (partial) style sheets to
reduce redundancy:

@example
  @@import url(http://www.style.org/pastoral);
  @@import url(http://www.style.org/marine);

  H1 @{ color: red @}     /* override imported sheets */
@end example
@item author/reader balance
Both readers and authors can influence the presentation through style
sheets. To do so, they use the same style sheet language thus reflecting
a fundamental feature of the web: everyone can become a publisher. The
@sc{ua} is free to choose the mechanism for referencing personal style
sheets.
@end table

Sometimes conflicts will arise between the style sheets that influence
the presentation. Conflict resolution is based on each style rule having
a weight. By default, the weights of the reader's rules are less than
the weights of rules in the author's documents. I.e., if there are
conflicts between the style sheets of an incoming document and the
reader's personal sheets, the author's rules will be used. Both reader
and author rules override the @sc{ua}'s default values.

The imported style sheets also cascade with each other, in the order
they are imported, according to the cascading rules defined below. Any
rules specified in the style sheet itself override rules in imported
style sheets. That is, imported style sheets are lower in the cascading
order than rules in the style sheet itself. Imported style sheets can
themselves import and override other style sheets, recursively.

In @sc{css1}, all '@@import' statements must occur at the start of a
style sheet, before any declarations. This makes it easy to see that
rules in the style sheet itself override rules in the imported style
sheets.

NOTE: The use of !important in @sc{css} stylesheets is unsupported at
this time.

Conflicting rules are intrinsic to the CSS mechanism. To find the value
for an element/property combination, the following algorithm must be
followed:

@enumerate
@item
Find all declarations that apply to the element/property in
question. Declarations apply if the selector matches the element in
question. If no declarations apply, the inherited value is used. If
there is no inherited value (this is the case for the 'HTML' element and
for properties that do not inherit), the initial value is used.
@item 
Sort the declarations by explicit weight: declarations marked
'!important' carry more weight than unmarked (normal) declarations.
@item
Sort by origin: the author's style sheets override the reader's style
sheet which override the UA's default values. An imported style sheet
has the same origin as the style sheet from which it is imported.
@item
Sort by specificity of selector: more specific selectors will override
more general ones. To find the specificity, count the number of ID
attributes in the selector (a), the number of CLASS attributes in the
selector (b), and the number of tag names in the selector
(c). Concatenating the three numbers (in a number system with a large
base) gives the specificity. Some examples:
@example
  LI            @{...@}  /* a=0 b=0 c=1 -> specificity =   1 */
  UL LI         @{...@}  /* a=0 b=0 c=2 -> specificity =   2 */
  UL OL LI      @{...@}  /* a=0 b=0 c=3 -> specificity =   3 */
  LI.red        @{...@}  /* a=0 b=1 c=1 -> specificity =  11 */
  UL OL LI.red  @{...@}  /* a=0 b=1 c=3 -> specificity =  13 */ 
  #x34y         @{...@}  /* a=1 b=0 c=0 -> specificity = 100 */ 
@end example
Pseudo-elements and pseudo-classes are counted as normal elements and
classes, respectively.
@item
Sort by order specified: if two rules have the same weight, the latter
specified wins. Rules in imported style sheets are considered to be
before any rules in the style sheet itself.
@end enumerate

The search for the property value can be terminated whenever one rule
has a higher weight than the other rules that apply to the same
element/property combination.

This strategy gives author's style sheets considerably higher weight
than those of the reader. It is therefore important that the reader has
the ability to turn off the influence of a certain style sheet,
e.g. through a pull-down menu.

A declaration in the 'STYLE' attribute of an element has the same weight
as a declaration with an ID-based selector that is specified at the end
of the style sheet:

@example
<STYLE TYPE="text/css">
  #x97z @{ color: blue @}
</STYLE>

<P ID=x97z STYLE="color: red">
@end example

In the above example, the color of the 'P' element would be
red. Although the specificity is the same for both declarations, the
declaration in the 'STYLE' attribute will override the one in the
'STYLE' element because of cascading rule number 5.

The @sc{ua} may choose to honor other stylistic @sc{html} attributes,
for example 'ALIGN'. If so, these attributes are translated to the
corresponding @sc{css} rules with specificity equal to 1. The rules are
assumed to be at the start of the author style sheet and may be
overridden by subsequent style sheet rules. In a transition phase, this
policy will make it easier for stylistic attributes to coexist with
style sheets.

@node Properties, Units, The Cascade, Stylesheets
@section Properties

In the text below, the allowed values for each property are listed
with a syntax like the following:

@example
      Value: N | NW | NE
      Value: [ <length> | thick | thin ]@{1,4@}
      Value: <uri>? <color> [ / <color> ]?
      Value: <uri> || <color>
@end example

The words between < and > give a type of value. The most common types
are <length>, <percentage>, <url>, <number>and <color> these are
described in the section on [[units]]. The more specialized types
(e.g. <font-family>and <border-style>) are described under the property
where they appear.

Other words are keywords that must appear literally, without quotes. The
slash (/) and the comma (,) must also appear literally.

Several things juxtaposed mean that all of them must occur, in the given
order. A bar (|) separates alternatives: one of them must occur. A
double bar (A || B) means that either A or B or both must occur, in any
order. Brackets ([]) are for grouping. Juxtaposition is stronger than
the double bar, and the double bar is stronger than the bar. Thus "a b |
c || d e" is equivalent to "[ a b ] | [ c || [ d e ]]".

Every type, keyword, or bracketed group may be followed by one of the
following modifiers:

@itemize @bullet
@item
An asterisk (*) indicates that the preceding type, word or group is
repeated zero or more times.
@item
A plus (+) indicates that the preceding type, word or group is repeated
one or more times.
@item
A question mark (?) indicates that the preceding type, word or group is
optional.
@item
A pair of numbers in curly braces (@{A,B@}) indicates that the preceding
type, word or group is repeated at least A and at most B times.
@end itemize

Other than the value the following information is also shown.

@multitable @columnfractions .3 .7
@item Supported Values: @tab If this is present, it lists the parts of
the specification that Emacs/W3 currently supports.
@item Unsupported Values: @tab If this is present, it represents the
parts of the specifcation that Emacs/W3 does not support.
@item Initial: @tab The default value for the property, unless
explicitly set in a stylesheet.
@item Applies to: @tab What type of elements this property can be attached to.
@item Inherited: @tab Yes or no
@item Percentage values: @tab What a percentage value applies to when given.
@end multitable

@menu
* Font Properties::             Selecting fonts, styles, and sizes.
* Colors and Backgrounds::      Controlling colors, front and back.
* Text Properties::             Alignment, decoration, and more!
* Box Properties::              Borders, padding, and margins, oh my!
* Classification::              Changing whitespace and display policies.
* Media Selection::             Conditionalize stylesheets on media-type.
* Speech Properties::           Speech output controlled by stylesheets.
@end menu

@node Font Properties, Colors and Backgrounds, Properties, Properties
@subsection Font Properties

Setting font properties will be among the most common uses of style
sheets.  Unfortunately, there exists no well-defined and universally
accepted taxonomy for classifying fonts, and terms that apply to one
font family may not be appropriate for others. E.g. 'italic' is commonly
used to label slanted text, but slanted text may also be labeled as
being @b{Oblique}, @b{Slanted}, @b{Incline}, @b{Cursive} or
@b{Kursiv}. Therefore it is not a simple problem to map typical font
selection properties to a specific font.

The properties defined by CSS1 are described in the following sections.
@menu
* font-family::                 Groups of fonts.
* font-style::                  Normal, italic, or oblique?
* font-variant::                Small-caps, etc.
* font-weight::                 How bold can you go?
* font-size::                   How big is yours?
* font::                        Shorthand for all of the above.
@end menu

@node font-family, font-style, Font Properties, Font Properties
@subsubsection font-family

@multitable @columnfractions .20 .8
@item Supported Values: @tab [[<family-name> | <generic-family>],]* [<family-name> | <generic-family>]
@item Initial: @tab User specific
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable
The value is a prioritized list of font family names and/or generic
family names. Unlike most other CSS1 properties, values are separated
by a comma to indicate that they are alternatives:

@example
  BODY @{ font-family: gill, helvetica, sans-serif @}
@end example

There are two types of list values:

@table @b
@item <family-name>
The name of a font family of choice. In the last example, "gill" and
"helvetica" are font families.
@item <generic-family>
In the example above, the last value is a generic family name. The
following generic families are defined:
@itemize @bullet
@item
'serif' (e.g. Times)
@item
'sans-serif' (e.g. Helvetica)
@item
'cursive' (e.g. Zapf-Chancery)
@item
'fantasy' (e.g. Western)
@item
'monospace' (e.g. Courier)
@end itemize
@end table

Style sheet designers are encouraged to offer a generic font family as a
last alternative.

Font names containing whitespace should be quoted:

@example
  BODY @{ font-family: "new century schoolbook", serif @}
  
  <BODY STYLE="font-family: 'My own font', fantasy">
@end example

If quoting is omitted, any whitespace characters before and after the
font name are ignored and any sequence of whitespace characters inside
the font name is converted to a single space.

@node font-style, font-variant, font-family, Font Properties
@subsubsection font-style

@multitable @columnfractions .2 .8
@item Supported Values: @tab normal | italic | oblique
@item Initial: @tab normal
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

The 'font-style' property selects between normal (sometimes referred to
as "roman" or "upright"), italic and oblique faces within a font family.

A value of 'normal' selects a font that is classified as 'normal' in the
UA's font database, while 'oblique' selects a font that is labeled
'oblique'. A value of 'italic' selects a font that is labeled 'italic',
or, if that is not available, one labeled 'oblique'.

The font that is labeled 'oblique' in the UA's font database may
actually have been generated by electronically slanting a normal font.

Fonts with Oblique, Slanted or Incline in their names will typically be
labeled 'oblique' in the UA's font database. Fonts with Italic, Cursive
or Kursiv in their names will typically be labeled 'italic'.

@example
  H1, H2, H3 @{ font-style: italic @}
  H1 EM @{ font-style: normal @}
@end example

In the example above, emphasized text within 'H1' will appear in a
normal face.

@node font-variant, font-weight, font-style, Font Properties
@subsubsection font-variant

@multitable @columnfractions .2 .8
@item Value:             @tab normal | small-caps
@item Initial:           @tab normal
@item Applies to:        @tab all elements
@item Inherited:         @tab yes
@item Percentage values: @tab N/A
@end multitable

Another type of variation within a font family is the small-caps. In a
small-caps font the lower case letters look similar to the uppercase
ones, but in a smaller size and with slightly different proportions. The
'font-variant' property selects that font.

A value of 'normal' selects a font that is not a small-caps font,
'small-caps' selects a small-caps font. It is acceptable (but not
required) in CSS1 if the small-caps font is a created by taking a normal
font and replacing the lower case letters by scaled uppercase
characters. As a last resort, uppercase letters will be used as
replacement for a small-caps font.

The following example results in an 'H3' element in small-caps, with
emphasized words in oblique small-caps:

@example
  H3 @{ font-variant: small-caps @}
  EM @{ font-style: oblique @}
@end example

There may be other variants in the font family as well, such as fonts
with old-style numerals, small-caps numerals, condensed or expanded
letters, etc. CSS1 has no properties that select those.

@node font-weight, font-size, font-variant, Font Properties
@subsubsection font-weight

@multitable @columnfractions .3 .7
@item Supported Values: @tab normal | bold | 100 | 200 | 300 | 400 | 500 | 600 | 700 | 800 | 900
@item Unsupported Values: @tab bolder | lighter
@item Initial: @tab normal
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

The 'font-weight' property selects the weight of the font. The values
'100' to '900' form an ordered sequence, where each number indicates a
weight that is at least as dark as its predecessor. The keyword 'normal'
is synonymous with '400', and 'bold' is synonymous with '700'. Keywords
other than 'normal' and 'bold' have been shown to be often confused with
font names and a numerical scale was therefore chosen for the 9-value
list.

@example
  P @{ font-weight: normal @}   /* 400 */
  H1 @{ font-weight: 700 @}     /* bold */
@end example

The 'bolder' and 'lighter' values select font weights that are relative
to the weight inherited from the parent:

@example
  STRONG @{ font-weight: bolder @}
@end example

There is no guarantee that there will be a darker face for each of the
'font-weight' values; for example, some fonts may have only a normal and
a bold face, others may have eight different face weights. There is no
guarantee on how a UA will map font faces within a family to weight
values. The only guarantee is that a face of a given value will be no
less dark than the faces of lighter values.

@node font-size, font, font-weight, Font Properties
@subsubsection font-size

@multitable @columnfractions .3 .7
@item Supported Values: @tab <absolute-size> | <length>
@item Unsupported Values: @tab <percentage> | <relative-size>
@item Initial: @tab medium
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab relative to parent element's font size
@end multitable

@table @b
@item <absolute-size>
An <absolute-size> keyword is an index to a table of font sizes computed
and kept by the UA. Possible values are:
@itemize @bullet
@item
xx-small
@item
x-small
@item
small
@item
medium
@item
large
@item
x-large
@item
xx-large
@end itemize

On a computer screen a scaling factor of 1.5 is suggested between
adjacent indexes; if the 'medium' font is 10pt, the 'large' font could
be 15pt. Different media may need different scaling factors. Also, the
UA should take the quality and availability of fonts into account when
computing the table. The table may be different from one font family to
another.
@item <relative-size>
A <relative-size> keyword is interpreted relative to the table of font
sizes and the font size of the parent element. Possible values are
@b{larger} or @b{smaller}. For example, if the parent element has a font
size of 'medium', a value of 'larger' will make the font size of the
current element be 'large'. If the parent element's size is not close to
a table entry, the UA is free to interpolate between table entries or
round off to the closest one. The UA may have to extrapolate table
values if the numerical value goes beyond the keywords.
@end table

Length and percentage values should not take the font size table into
account when calculating the font size of the element.

Negative values are not allowed.

On all other properties, 'em' and 'ex' length values refer to the font
size of the current element. On the 'font-size' property, these length
units refer to the font size of the parent element.

Note that an application may reinterpret an explicit size, depending on
the context. E.g., inside a VR scene a font may get a different size
because of perspective distortion.

Examples:

@example
  P @{ font-size: 12pt; @}
  BLOCKQUOTE @{ font-size: larger @}
  EM @{ font-size: 150% @}
  EM @{ font-size: 1.5em @}
@end example

If the suggested scaling factor of 1.5 is used, the last three
declarations are identical.

@node font,  , font-size, Font Properties
@subsubsection font

@multitable @columnfractions .2 .8
@item Value: @tab [ <font-style> || <font-variant> || <font-weight> ]? <font-size> [ / <line-height> ]? <font-family>
@item Initial: @tab not defined for shorthand properties
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab allowed on <font-size> and <line-height>
@end multitable
The 'font' property is a shorthand property for setting 'font-style'
'font-variant' 'font-weight' 'font-size', 'line-height' and
'font-family' at the same place in the style sheet. The syntax of this
property is based on a traditional typographical shorthand notation to
set multiple properties related to fonts.

For a definition of allowed and initial values, see the previously
defined properties. Properties for which no values are given are set to
their initial value.

@example
  P @{ font: 12pt/14pt sans-serif @}
  P @{ font: 80% sans-serif @}
  P @{ font: x-large/110% "new century schoolbook", serif @}
  P @{ font: bold italic large Palatino, serif @}
  P @{ font: normal small-caps 120%/120% fantasy @}
@end example

In the second rule, the font size percentage value ('80%') refers to the
font size of the parent element. In the third rule, the line height
percentage refers to the font size of the element itself.

In the first three rules above, the 'font-style', 'font-variant' and
'font-weight' are not explicitly mentioned, which means they are all
three set to their initial value ('normal'). The fourth rule sets the
'font-weight' to 'bold', the 'font-style' to 'italic' and implicitly
sets 'font-variant' to 'normal'.

The fifth rule sets the 'font-variant' ('small-caps'), the 'font-size'
(120% of the parent's font), the 'line-height' (120% times the font
size) and the 'font-family' ('fantasy'). It follows that the keyword
'normal' applies to the two remaining properties: 'font-style' and
'font-weight'.

@node Colors and Backgrounds, Text Properties, Font Properties, Properties
@subsection Colors and Backgrounds

These properties describe the color (often called foreground color) and
background of an element (i.e. the surface onto which the content is
rendered). One can set a background color and/or a background image. The
position of the image, if/how it is repeated, and whether it is fixed or
scrolled relative to the canvas can also be set.

The 'color' property inherits normally. The background properties do not
inherit, but the parent element's background will shine through by
default because of the initial 'transparent' value on
'background-color'.

NOTE: Currently, Emacs/W3 can only show background images under XEmacs.
Emacs 19 doesn't have the support in its display code yet.

@menu
* color::                       Foreground colors.
* background-color::            Background colors.
* background-image::            Background images.
* background-repeat::           Controlling repeating of background images.
* background-attachment::       Where background images are drawn.
* background-position::         Where background images are drawn.
* background::                  Shorthand for all background properties.
@end menu

@node color, background-color, Colors and Backgrounds, Colors and Backgrounds
@subsubsection color

@multitable @columnfractions .2 .8
@item Value: @tab <color>
@item Initial: @tab User specific
@item Applies to: @tab  all elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

This property describes the text color of  an element (often referred to
as the foreground color). There are different ways to specify red:

@example
  EM @{ color: red @}              /* natural language */
  EM @{ color: rgb(255,0,0) @}     /* RGB range 0-255   */
@end example

See @ref{Color Units} for a description of possible color values.

@node background-color, background-image, color, Colors and Backgrounds
@subsubsection background-color

@multitable @columnfractions .2 .8
@item Value: @tab <color> | transparent
@item Initial: @tab transparent
@item Applies to: @tab all elements
@item Inherited: @tab no
@item Percentage values: @tab N/A
@end multitable

This property sets the background color of an element.

@example
  H1 @{ background-color: #F00 @}
@end example

@node background-image, background-repeat, background-color, Colors and Backgrounds
@subsubsection background-image

@multitable @columnfractions .2 .8
@item Value: @tab <url> | none
@item Initial: @tab none
@item Applies to: @tab all elements
@item Inherited: @tab no
@item Percentage values: @tab N/A
@end multitable

This property sets the background image of an element. When setting a
background image, one should also set a background color that will be
used when the image is unavailable. When the image is available, it is
overlaid on top of the background color.

@example
  BODY @{ background-image: url(marble.png) @}
  P @{ background-image: none @}
@end example

@node background-repeat, background-attachment, background-image, Colors and Backgrounds
@subsubsection background-repeat

This property is not supported at all under Emacs/W3.

@node background-attachment, background-position, background-repeat, Colors and Backgrounds
@subsubsection background-attachment

This property is not supported at all under Emacs/W3.

@node background-position, background, background-attachment, Colors and Backgrounds
@subsubsection background-position

This property is not supported at all under Emacs/W3.

@node background,  , background-position, Colors and Backgrounds
@subsubsection background

@multitable @columnfractions .2 .8
@item Value: @tab <background-color> || <background-image> || <background-repeat> || <background-attachment> || <background-position>
@item Initial: @tab not defined for shorthand properties
@item Applies to: @tab all elements
@item Inherited: @tab no
@item Percentage values: @tab allowed on <background-position>
@end multitable

The 'background' property is a shorthand property for setting the
individual background properties (i.e., 'background-color',
'background-image', 'background-repeat', 'background-attachment' and
'background-position') at the same place in the style sheet.

Possible values on the 'background' properties are the set of all
possible values on the individual properties.

@example 
  BODY @{ background: red @}
  P @{ background: url(chess.png) gray 50% repeat fixed @}
@end example

The 'background' property always sets all the individual background
properties. In the first rule of the above example, only a value for
'background-color' has been given and the other individual properties
are set to their initial value. In the second rule, all individual
properties have been specified.

@node Text Properties, Box Properties, Colors and Backgrounds, Properties
@subsection Text Properties

@menu
* word-spacing::                
* letter-spacing::              
* text-decoration::             
* vertical-align::              
* text-transform::              
* text-align::                  
* text-indent::                 
* line-height::                 
@end menu

@node word-spacing, letter-spacing, Text Properties, Text Properties
@subsubsection word-spacing

@multitable @columnfractions .3 .7
@item Supported Values: @tab normal
@item Unsupported Values: @tab <length>
@item Initial: @tab normal
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

The length unit indicates an addition to the default space between
words. Values can be negative, but there may be implementation-specific
limits. The UA is free to select the exact spacing algorithm. The word
spacing may also be influenced by justification (which is a value of the
'align' property).

@example
  H1 @{ word-spacing: 0.4em @}
@end example

Here, the word-spacing between each word in 'H1' elements would be
increased by '1em'.

NOTE: Emacs/W3 cannot currently support this, due to limitations in
Emacs.  It may  be implemented in the future.

@node letter-spacing, text-decoration, word-spacing, Text Properties
@subsubsection letter-spacing

@multitable @columnfractions .3 .7
@item Supported Values: @tab normal
@item Unsupported Values: @tab <length>
@item Initial: @tab normal
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

The length unit indicates an addition to the default space between
characters. Values can be negative, but there may be
implementation-specific limits. The UA is free to select the exact
spacing algorithm. The letter spacing may also be influenced by
justification (which is a value of the 'align' property).

@example
  BLOCKQUOTE @{ letter-spacing: 0.1em @}
@end example

Here, the letter-spacing between each character in 'BLOCKQUOTE' elements
would be increased by '0.1em'.

NOTE: Emacs/W3 cannot currently support this, due to limitations in
Emacs.  It may be implemented in the future.

@node text-decoration, vertical-align, letter-spacing, Text Properties
@subsubsection text-decoration

@multitable @columnfractions .3 .7
@item Supported Values: @tab none | underline | line-through | blink
@item Unsupported Values: @tab overline 
@item Initial: @tab none
@item Applies to: @tab all elements
@item Inherited: @tab no, but see clarification below
@item Percentage values: @tab N/A
@end multitable

This property describes decorations that are added to the text of an
element. If the element has no text (e.g. the 'IMG' element in HTML) or
is an empty element (e.g. '<EM></EM>'), this property has no effect. A
value of 'blink' causes the text to blink.

The color(s) required for the text decoration should be derived from the
'color' property value.

This property is not inherited, but elements should match their
parent. E.g., if an element is underlined, the line should span the
child elements. The color of the underlining will remain the same even
if descendant elements have different 'color' values.

@example
  A:link, A:visited, A:active @{ text-decoration: underline @}
@end example

The example above would underline the text of all links (i.e., all 'A'
elements with a 'HREF' attribute).

NOTE: The 'line-through' property is only supported under XEmacs
currently.  A patch has been sent to the Emacs maintainers to add
support for this, but it has not made it into the main distribution
yet.

@node vertical-align, text-transform, text-decoration, Text Properties
@subsubsection vertical-align

This is currently unsupported in Emacs/W3.

@node text-transform, text-align, vertical-align, Text Properties
@subsubsection text-transform

@multitable @columnfractions .3 .7
@item Supported Values: @tab none
@item Unsupported Values: @tab capitalize | uppercase | lowercase
@item Initial: @tab none
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

@table @b
@item 'capitalize'
Uppercases the first character of each word.
@item 'uppercase'
Uppercases all letters of the element.
@item 'lowercase'
Lowercases all letters of the element.
@item 'none'
Neutralizes inherited value.
@end table

The actual transformation in each case is human language dependent.

@example
  H1 @{ text-transform: uppercase @}
@end example

The example above would put 'H1' elements in uppercase text.

NOTE: This capability was in the previous version of Emacs/W3, but has
not been reimplemented in the new display code yet.  Please feel free to
send me patches.

@node text-align, text-indent, text-transform, Text Properties
@subsubsection text-align

@multitable @columnfractions .2 .8
@item Value: @tab left | right | center | justify
@item Initial: @tab User specific
@item Applies to: @tab block-level elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

This property describes how text is aligned within the element. The
actual justification algorithm used is UA and human language dependent.

Example:
@example
  DIV.center @{ text-align: center @}
@end example

Since 'text-align' inherits, all block-level elements inside the 'DIV'
element with 'CLASS=center' will be centered. Note that alignments are
relative to the width of the element, not the canvas.

@node text-indent, line-height, text-align, Text Properties
@subsubsection text-indent

Not currently implemented in Emacs/W3.

@node line-height,  , text-indent, Text Properties
@subsubsection line-height

Not currently implemented in Emacs/W3.

@node Box Properties, Classification, Text Properties, Properties
@subsection Box Properties

@multitable @columnfractions .2 .8
@end multitable

@node Classification, Media Selection, Box Properties, Properties
@subsection Classification

These properties classify elements into categories more than they set
specific visual parameters.

The list-style properties describe how list items (i.e. elements with a
'display' value of 'list-item') are formatted. The list-style properties
can be set on any element, and it will inherit normally down the
tree. However, they will only be have effect on elements with a
'display' value of 'list-item'. In HTML this is typically the case for
the 'LI' element.

@menu
* display::                     
* white-space::                 
* list-style-type::             
* list-style-image::            
* list-style-position::         
* list-style::                  
@end menu

@node display, white-space, Classification, Classification
@subsubsection display

@multitable @columnfractions .2 .8
@item Value: @tab block | inline | list-item | none
@item Extensions: @tab line
@item Initial: @tab inline
@item Applies to: @tab all elements
@item Inherited: @tab no
@item Percentage values: @tab N/A
@end multitable

This property describes how/if an element is displayed on the canvas
(which may be on a printed page, a computer display etc.).

An element with a 'display' value of 'block' opens whitespace suitable
for a paragraph break.  Typically, elements like 'H1' and 'P' are of
type 'block'. A value of 'list-item' is similar to 'block' except that a
list-item marker is added. In HTML, 'LI' will typically have this value.

An element with a 'display' value of 'inline' results in a new inline
box on the same line as the previous content.

A value of 'none' turns off the display of the element, including
children elements and the surrounding box.

@example
  P @{ display: block @}
  EM @{ display: inline @}
  LI @{ display: list-item @}
  IMG @{ display: none @}
@end example

The last rule turns off the display of images.

A value of 'line' results in a single line break.  Emacs/W3 needs this
extension to be able to fully specify the behaviour of @sc{br} and
@sc{hr} elements within a stylesheet.

NOTE: Emacs/W3 defaults to using 'inline' for this property, which is a
slight deviation from the specification.

@node white-space, list-style-type, display, Classification
@subsubsection white-space

@multitable @columnfractions .2 .8
@item Value: @tab normal | pre | nowrap
@item Initial: @tab normal
@item Applies to: @tab block-level elements
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

This property declares how whitespace inside the element is handled: the
'normal' way (where whitespace is collapsed), as 'pre' (which behaves
like the 'PRE' element in HTML) or as 'nowrap' (where wrapping is done
only through BR elements):

@example
  PRE @{ white-space: pre @}
  P   @{ white-space: normal @}
@end example

@node list-style-type, list-style-image, white-space, Classification
@subsubsection list-style-type

@multitable @columnfractions .2 .8
@item Value: @tab disc | circle | square | decimal | lower-roman | upper-roman | lower-alpha | upper-alpha | none
@item Initial: @tab disc
@item Applies to: @tab elements with 'display' value 'list-item'
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

This property is used to determine the appearance of the list-item
marker if 'list-style-image' is 'none' or if the image pointed to by the
URL cannot be displayed.

Fo example:
@example
  OL @{ list-style-type: decimal @}       /* 1 2 3 4 5 etc. */
  OL @{ list-style-type: lower-alpha @}   /* a b c d e etc. */
  OL @{ list-style-type: lower-roman @}   /* i ii iii iv v etc. */
@end example

@node list-style-image, list-style-position, list-style-type, Classification
@subsubsection list-style-image

@multitable @columnfractions .2 .8
@item Value: @tab <url> | none
@item Initial: @tab none
@item Applies to: @tab elements with 'display' value 'list-item'
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

This property sets the image that will be used as the list-item
marker. When the image is available it will replace the marker set with
the 'list-style-type' marker.

NOTE: This is currently unimplemented in Emacs/W3.

@example
  UL @{ list-style-image: url(http://png.com/ellipse.png) @}
@end example

@node list-style-position, list-style, list-style-image, Classification
@subsubsection list-style-position

@multitable @columnfractions .3 .7
@item Supported Values: @tab outside
@item Unsupported Values: @tab inside
@item Initial: @tab outside
@item Applies to: @tab elements with 'display' value 'list-item'
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

The value of 'list-style-position' determines how the list-item marker
is drawn with regard to the content. For a formatting example see
section 4.1.3.

@node list-style,  , list-style-position, Classification
@subsubsection list-style

@multitable @columnfractions .2 .8
@item Value: @tab <keyword> || <position> || <url>
@item Initial: @tab not defined for shorthand properties
@item Applies to: @tab elements with 'display' value 'list-item'
@item Inherited: @tab yes
@item Percentage values: @tab N/A
@end multitable

The 'list-style' property is a shorthand notation for setting the three
properties 'list-style-type', 'list-style-image' and
'list-style-position' at the same place in the style sheet.

@example
  UL @{ list-style: upper-roman inside @}
  UL UL @{ list-style: circle outside @}
  LI.square @{ list-style: square @}
@end example

Setting 'list-style' directly on 'LI' elements can have unexpected
results. Consider:

@example
  <STYLE TYPE="text/css">
    OL.alpha LI  @{ list-style: lower-alpha @}
    UL LI        @{ list-style: disc @}
  </STYLE>
  <BODY>
    <OL CLASS=alpha>
      <LI>level 1
      <UL>
         <LI>level 2
      </UL>
    </OL>
  </BODY>
@end example

Since the specificity (as defined in the cascading order) is higher for
the first rule in the style sheet in the example above, it will override
the second rule on all 'LI' elements and only 'lower-alpha' list styles
will be used. It is therefore recommended to set 'list-style' only on
the list type elements:

@example
  OL.alpha  @{ list-style: lower-alpha @}
  UL        @{ list-style: disc @}
@end example

In the above example, inheritance will transfer the 'list-style' values
from 'OL' and 'UL' elements to 'LI' elements.

A URL value can be combined with any other value:

@example
  UL @{ list-style: url(http://png.com/ellipse.png) disc @}
@end example

In the example above, the 'disc' will be used when the image is
unavailable.

@node Media Selection, Speech Properties, Classification, Properties
@subsection Media Selection

To specify that a stylesheet declaration should only apply when using a
certain media type (ie: different font families preferred when printing
versus on-screen presentation), the declarations should be wrapped in
the proposed @b{@@media} directive.

The @@media directive takes two arguments, the media type, and a block
of style declarations.

@example
  @@media print @{ 
    BODY @{ font-size: 10pt @}
    H1 @{ font-size: 14pt @}
  @}
@end example
The '@@media' construct also allows to put include style sheet rules
for various media in the same style sheet:

@example
  @@media print @{
    BODY @{ font-size: 10pt @}
  @}
  @@media screen @{
    BODY @{ font-size: 12pt @}
  @}
@end example

Currently, the following media types are defined.
@table @b
@item Print
Output for paged opaque material, and for documents viewed on screen in
print preview mode.
@item Screen
A continuous presentation for computer screens.
@item Projector
Paged presentation for projected presentations.
@item Braille
For braille tactile feedback devices.
@item Speech
Aural presentation.
@item Light
The stylesheet will only be applied if the user is using a light background.
@item Dark
The stylesheet will only be applied if the user is using a dark background.
@item Emacs
The stylesheet will only be applied if the user is running in Emacs 19.
@item XEmacs
The stylesheet will only be applied if the user is running in XEmacs 19.
@item All
The default value, the style sheet applies to all output devices.
@end table

@node Speech Properties,  , Media Selection, Properties
@subsection Speech Properties

Those of us who are sighted are accustomed to visual presentation of
@sc{html} documents, frequently on a bitmapped display. This is not the
only possible presentation method, however. Aural presentation, using a
combination of speech synthesis and 'audio icons', provides an
alternative presentation. This form of presentation is in current use by
the blind and print-impaired communities.

Often such aural presentation occurs by converting the document to plain
text and feeding this to a 'screen reader' -- software or hardware that
simply reads all the characters on the screen. This results in less
effective presentation than would be the case if the document structure
were retained.

There are other large markets for aural presentation, including in-car
and home entertainment use; aurual or mixed aural/visual presentation is
thus likely to increase in importance over the next few years. Realizing
that that the aural rendering is essentially independent of the visual
rendering:

@itemize @bullet
@item
Allows orthogonal aural and visual views.
@item
Allows browsers to optionally implement both aural and visual views to
produce truly multimodal documents.
@end itemize

@menu
* volume::                      
* pause-before::                
* pause-after::                 
* pause::                       
* cue-before::                  
* cue-after::                   
* cue::                         
* play-during::                 
* speed::                       
* voice-family::                
* pitch::                       
* pitch-range::                 
* stress::                      
* richness::                    
* speak-punctuation::           
* speak-date::                  
* speak-numeral::               
* speak-time::                  
@end menu

@node volume, pause-before, Speech Properties, Speech Properties
@subsubsection volume

@multitable @columnfractions .2 .8
@item Value: @tab <percentage> | mute | x-soft | soft | medium | loud | x-loud
@item Initial: @tab medium
@item Applies to: @tab all elements
@item Inherited: @tab yes
@item Percentage values: @tab relative to user-specified mapping
@end multitable

The legal range of percentage values is 0% to 100%. There is a fixed
mapping between keyword values and percentages:

@itemize @bullet
@item
'x-soft' = '0%'
@item
'soft' = '25%'
@item
'medium' = '50%'
@item
'loud' = '75%'
@item
'x-loud' = '100%'
@end itemize

Volume refers to the median volume of the waveform. In other words, a
highly inflected voice at a volume of 50 might peak well above
that. Note that '0%' does not mean the same as "mute". 0% represents the
minimum audible volume level and 100% corresponds to the maximum
comfortable level. The UA should allow the values corresponding to 0%
and 100% to be set by the user. Suitable values depend on the equipment
in use (speakers, headphones), the environment (in car, home theater,
library) and personal preferences. Some examples:

@itemize @bullet
@item
A browser for in-car use has a setting for when there is lots of
background noise . 0% would map to a fairly high level and 100% to a
quite high level. The overall values are likely to be human adjustable
for comfort, for example with a physical volume control: what this
proposal does is adjust the dynamic range.
@item
Another speech browser is being used in the home, late at night, (don't
annoy the neighbors) or in a shared study room. 0% is set to very quiet
and 100% to a fairly quiet level, too. As with the first example, there
is a low slope; the dynamic range is reduced. The actual volumes are low
here, wheras they were high in the first example.
@item
In a quiet and isolated house, an expensive hifi home theatre setup. 0%
is set fairly low and 100% to quite high; there is wide dynamic range.
@end itemize

The same authors stylesheet could be used in all cases, simply by
mapping the 0 and 100 points suitably at the client side.

@node pause-before, pause-after, volume, Speech Properties
@subsubsection pause-before

@multitable @columnfractions .2 .8
@item Value: @tab <time> | <percentage>
@item Initial: @tab UA specific
@item Applies to: @tab all elements
@item Inherited: @tab no
@item Percentage values: @tab speed
@end multitable

This property specifies the pause before elements. It may be given in an
absolute units (seconds, milliseconds) or as a relative value in which
case it is relative to the reciprocal of the 'speed' property: if speed
is 120 words per minute (ie a word takes half a second -- 500
milliseconds) then a pause-before of 100% means a pause of 500 ms and a
pause-before of 20% means 100ms.

Using relative units gives more robust stylesheets in the face of large
changes in speed.

@node pause-after, pause, pause-before, Speech Properties
@subsubsection pause-after

@multitable @columnfractions .2 .8
@item Value: @tab <time> | <percentage>
@item Applies to: @tab all elements
@item Inherited: @tab no
@item Percentage values: @tab speed
@end multitable

This property specifies the pause after elements. Values are specified
the same way as 'pause-before'.

@node pause, cue-before, pause-after, Speech Properties
@subsubsection pause

@multitable @columnfractions .2 .8
@item Value: @tab [<time> | <percentage> ]@{1,2@};
@item Applies to: @tab all elements
@item Inherited: @tab no
@item Percentage values: @tab speed
@end multitable

The 'pause' property is a shorthand for setting 'pause-before' and
'pause-after'. The first value is pause-before and the second is
pause-after. If only one value is given, it applies to both properties.

Examples:

@example
  H1 @{ pause: 20ms @}       /* pause-before: 20ms; pause-after: 20ms */
  H2 @{ pause: 30ms 40ms @}  /* pause-before: 30ms; pause-after: 40ms */
  H3 @{ pause-after: 10ms @} /* pause-before: ?;    pause-after: 10ms */
@end example

@node cue-before, cue-after, pause, Speech Properties
@subsubsection cue-before

@multitable @columnfractions .2 .8
@item Value: @tab <url> | none
@item Initial: @tab none
@item Applies to: @tab all elements
@item Inherited: @tab no
@end multitable
Auditory icons are another way to distinguish semantic elements. Sounds
may be played before, and/or after the element to delimit it. The same
sound can be used both before and after, using the cue property.

Examples:

@example
  A  @{ cue-before: url(bell.aiff); cue-after: url(dong.wav) @}
  H1 @{ cue-before: url(pop.au); cue-after: url(pop.au) @}
  H1 @{ cue: url(pop.au) @}  /* same as previous */
@end example

@node cue-after, cue, cue-before, Speech Properties
@subsubsection cue-after

@xref{cue-before}.

@node cue, play-during, cue-after, Speech Properties
@subsubsection cue

@xref{cue-before}.

@node play-during, speed, cue, Speech Properties
@subsubsection cue-during

@multitable @columnfractions .2 .8
@item Value: @tab <url> | mix | none
@item Initial: @tab mix
@item Applies to: @tab all elements
@item Inherited: @tab no
@end multitable
Similar to the cue-before and cue-after properties, this indicates sound
to be played during an element as a background (ie the sound is mixed in
with the speech).

Examples:

@example
  BLOCKQUOTE.sad @{ cue-during: url(violins.aiff) @}
@end example

@node speed, voice-family, play-during, Speech Properties
@subsubsection speed

@multitable @columnfractions .2 .8
@item Value: @tab <words-per-minute> | x-slow | slow | medium | fast | x-fast | faster | slower
@item Initial: @tab medium
@item Applies to: @tab all elements
@item Inherited: @tab yes
@end multitable

Specifies the speaking rate. Note that both absolute and relative
keyword values are allowed (compare with @ref{font-weight}).

@node voice-family, pitch, speed, Speech Properties
@subsubsection voice-family

@multitable @columnfractions .2 .8
@item Value: @tab [[<specific-voice> | <generic-voice>],]* [<specific-voice> | <generic-voice>]
@item Initial: @tab device-specific
@item Applies to: @tab all elements
@item Inherited: @tab yes
@end multitable

The value is a prioritized list of voice family names. Generic families
are male, female, and child.

Examples of specific voice families are: comedian, paul, lisa

Examples

@example
  H1 @{ voice-family: announcer, male @}
  P.part.romeo @{ voice-family: romeo, male @}
  P.part.juliet @{ voice-family: juliet, female @}
@end example

@node pitch, pitch-range, voice-family, Speech Properties
@subsubsection pitch

@multitable @columnfractions .2 .8
@end multitable

@node pitch-range, stress, pitch, Speech Properties
@subsubsection pitch-range

@multitable @columnfractions .2 .8
@end multitable

@node stress, richness, pitch-range, Speech Properties
@subsubsection stress

@multitable @columnfractions .2 .8
@item Value: @tab <percentage>
@item Initial: @tab medium
@item Applies to: @tab all elements
@item Inherited: @tab yes
@end multitable

Specifies the level of stress (assertiveness or emphasis) of the
speaking voice. English is a stressed language, and different parts of a
sentence are assigned primary, secondary or tertiary stress. The value
of property 'stress' controls the amount of inflection that results from
these stress markers.

Increasing the value of this property results in the speech being more
strongly inflected. It is in a sense dual to property 'pitch-range' and
is provided to allow developers to exploit higher-end auditory displays.

@node richness, speak-punctuation, stress, Speech Properties
@subsubsection richness

@multitable @columnfractions .2 .8
@item Value: @tab <percentage>
@item Initial: @tab medium (50%)
@item Applies to: @tab all elements
@item Inherited: @tab yes
@end multitable

Specifies the richness (brightness) of the speaking voice. Different
speech devices may require the setting of one or more device-specific
parameters to achieve this effect.

The effect of increasing richness is to produce a voice that carries --
reducing richness produces a soft, mellifluous voice.

@node speak-punctuation, speak-date, richness, Speech Properties
@subsubsection speak-punctuation

@multitable @columnfractions .2 .8
@item Value: @tab code | none
@item Initial: @tab none
@item Applies to: @tab all elements
@item Inherited: @tab yes
@end multitable

'code' indicates that punctuation such as semicolons, braces, and so on
are to be spoken literally. The default value of 'none' means that
punctuation is not spoken but instead is rendered naturally as various
pauses.

@node speak-date, speak-numeral, speak-punctuation, Speech Properties
@subsubsection speak-date

@multitable @columnfractions .2 .8
@item Value: @tab myd | dmy | ymd | none
@item Initial: @tab none
@item Applies to: @tab all elements
@item Inherited: @tab no
@end multitable

This is a hint that the element contains a date and also how that date
should be spoken. month-day-year is common in the USA, while
day-month-year is common in Europe and year-month-day is also used.

This should really be an HTML tag not a stylesheet property, since it
gives semantic information about the content.

@node speak-numeral, speak-time, speak-date, Speech Properties
@subsubsection speak-numeral

@multitable @columnfractions .2 .8
@item Value: @tab digits | continous
@item Initial: @tab none
@item Applies to: @tab all elements
@item Inherited: @tab yes
@end multitable

@node speak-time,  , speak-numeral, Speech Properties
@subsubsection speak-time

@multitable @columnfractions .2 .8
@item Value: @tab 24 | 12 | none
@item Initial: @tab none
@item Applies to: @tab all elements
@item Inherited: @tab yes
@end multitable

@node Units,  , Properties, Stylesheets
@section Units

@menu
* Length Units::                
* Percentage Units::            
* Color Units::                 
* URLs::                        
* Angle Units::                 
* Time Units::                  
@end menu

@node Length Units, Percentage Units, Units, Units
@subsection Length Units

@node Percentage Units, Color Units, Length Units, Units
@subsection Percentage Units

@node Color Units, URLs, Percentage Units, Units
@subsection color Units

@node URLs, Angle Units, Color Units, Units
@subsection URLs

@node Angle Units, Time Units, URLs, Units
@subsection Angle Units

These are the legal angle units:
@itemize @bullet
@item
deg: degrees
@item
grad
@item
rad: radians
@end itemize

@node Time Units,  , Angle Units, Units
@subsection Time Units

These are the legal time units:

@itemize @bullet
@item
ms: milliseconds
@item
s: seconds
@end itemize

@node Supported URLs, MIME Support, Stylesheets, Top
@chapter Supported URLs

::WORK:: List supported URL types, specific RFCs, etc.

@dfn{Uniform Resource Locators} (@sc{url}s) are a specific form of
@dfn{Uniform Resource Identifiers} (@sc{uri}) described in @sc{rfc}2396
which updates @sc{rfc}1738 and @sc{rfc}1808.

@sc{rfc2016} defines uniform resource agents.

@sc{uri} have the form @var{scheme}:@var{scheme-specific-part}, where @var{scheme}
appears in the menu below for @sc{url}s supported by Emacs/W3.

@sc{ftp, nfs, http, https}, @code{rlogin}, @code{telnet}, tn3270,
@sc{irc} and gopher @sc{url}s all have the form
@var{scheme}://[@var{userinfo}@@]@var{hostname}[:@var{port}][/@var{path}]
where @samp{[} and @samp{]} delimit optional parts.  @var{userinfo}
sometimes takes the form @var{userinfo}:@var{password} but you should
beware of the security risks of sending cleartext passwords.
@var{hostname} may be a domain name or a dotted decimal address.  If the
@samp{:@var{port}} is omitted then Emacs/W3 will use the well known port
for that service.  With the possible exception of @code{telnet}, it is
very rare for ports to be specified, and it is possible using a
non-standard port may have undesired consequences if a different service
is listening on that port (eg. a gopher @sc{url} specifying the
@sc{smtp} port can cause mail to be sent), but @xref{Other Variables,
url-bad-port-list}.  The meaning of the @var{path} component depends on
the service.

@menu
* file::                        Local file access.
* ftp::                         Remote file access via ftp.
* nfs::                         Remote file access via NFS.
* info::                        Access to the Emacs Info system.
* http/https::                  @sc{http/1.0} support.
* mailto::                      Sending simple electronic mail.
* mailserver::                  Slightly more complicated electronic mail.
* news/nntp/snews::             Reading and sending Usenet news.
* rlogin/telnet/tn3270::        Legacy host connections.
* irc::                         Internet Relay Chat.
* data::                        Embedding the data within the URL itself.
* gopher::                      Gopher and Gopher+.
* finger::                      The old favorite.
* netrek::                      netrek.
@end menu

@node file, ftp, Supported URLs, Supported URLs
@section File @sc{url}s
@cindex files
@cindex File @sc{url}s

@vindex url-directory-index-file
This allows Emacs/W3 to read arbitary files from hosts.  Compressed
files are handled, but support is hard-coded so that
@code{jka-compr-compression-info-list} and so on have no affect.
Suffixes recognized are @samp{.z}, @samp{.gz} and @samp{.Z}.  If the
@sc{url} points to a directory, then it will try to retrieve a file
named by @code{url-directory-index-file} (@file{index.html} by default)
and parse it, otherwise you get a directory listing in @samp{dired}
mode.  If the @sc{url} refers to a file on a remote host, then Emacs/W3
uses @samp{ange-ftp} (@pxref{Top, , ange-ftp}) or @samp{efs}
(@pxref{Top, , efs}) to retrieve the file.  ftp:// and file:// are
synonymous for Emacs/W3.

@node ftp, nfs, file, Supported URLs
@section @sc{ftp} @sc{url}s
@cindex @sc{ftp}

For details of usage see @ref{file}.  In Emacs/W3 file and @sc{ftp} @sc{url}s
are synonymous and files on the localhost are retrieved directly rather
than by @sc{ftp}.  Emacs/W3 relies on @samp{ange-ftp}
(@pxref{Top, , ange-ftp}) or @samp{efs} (@pxref{Top, , efs}) to do the actual
transfers.

@node nfs, info, ftp, Supported URLs
@section @sc{nfs} @sc{url}s
@cindex @sc{nfs}
@cindex @sc{nfs} @sc{url}s

@vindex url-nfs-automounter-directory-spec
gdj1: have I misunderstood the point of this?
Since @sc{nfs} is fairly transparent to the user (at least when it's
working), there isn't very much to say here.  An nfs @sc{url} is similar
to a file @sc{url} except that it points to a file on a remote host that
is handled by the automounter on the local host.  The variable
@code{url-nfs-automounter-directory-spec} may need to be tweaked
depending on local configuration.  The @sc{nfs} @sc{url} is defined in
@sc{rfc2224}.

@node info, http/https, nfs, Supported URLs
@section info
@cindex info
@cindex info @sc{url}s
Info @sc{url}s are not an officially recognised @sc{url} (gdj1: is this
right?), but Emacs/W3 will parse them to produce a reference to a
TeXinfo node, or @samp{Top} if one is not specified.  @samp{Info-mode}
will be used to browse the document.

@node http/https, mailto, info, Supported URLs
@section http/https
@cindex @sc{http}
@cindex @sc{https}
@vindex url-honor-refresh-requests
@vindex url-be-anal-about-file-attributes
The HyperText Transfer Protocol is the protocol used to get documents
from the World Wide Web.  Emacs/W3 supports @sc{http} version 1.0 as
defined in @sc{rfc}1945 --- now superseded by version 1.1 defined in
@sc{rfc}2068.

If @code{url-honor-refresh-requests} is @code{nil} then @samp{Refresh}
headers will not be honoured, if @code{t} then they will always be
honoured, otherwise the user will be asked for each request.  The
default is @code{t}.  @code{url-be-anal-about-file-attributes} controls
whether @sc{http} is used to discover file attributes, or whether
they're just guessed.  The default is @code{nil} which means that
Emacs/W3 will make educated guesses.

@sc{https} is a secure version of @sc{http} defined in @sc{rfc}2069
(gdj1: ?).  Emacs/W3 requires @sc{ssl} to handle this, @xref{Installing SSL}.

@node mailto, mailserver, http/https, Supported URLs
@section mailto
@vindex url-mail-command
@cindex mailto
@cindex mailto @sc{url}s
A mailto @sc{url} will send an email message to the address in the
@sc{url}, for example @samp{mailto:foo@@bar.com} would compose a
message to foo@@bar.com.  Emacs/W3 uses the command specified by the
@code{url-mail-command} variable to compose the email, this is @code{url-mail} by
default which uses Gnu's @samp{message} mode (@pxref{Top, Message, , message}) if
available, otherwise the standard @code{mail} command.  An X-Url-From
header field containing the @sc{url} of the document that contained the
mailto @sc{url} is added, as is an X-Mailer header field containing the
version of Emacs/W3 being used.

@sc{rfc}2368 extends the definition of mailto @sc{url}s in @sc{rfc1738}.
The form of a mailto @sc{url} is
@samp{mailto:@var{mailbox}[?@var{header}=@var{contents}[&@var{header}=@var{contents}]]}
where an arbitary number of @var{header}s can be added.  If the
@var{header} is @samp{body}, then @var{contents} is put in the body
otherwise a @var{header} header field is created with @var{contents} as its
contents.  Note that Emacs/W3 does not consider any headers as
`dangerous' so you should check them before sending the message.

Email messages are defined in @sc{rfc}822.

@node mailserver, news/nntp/snews, mailto, Supported URLs
@section mailserver
@cindex mailserver
@cindex mailserver @sc{url}s
A mailserver @sc{url} allows you to send an email to a person, but this
@sc{url} optionally specifies a subject and a body.  The basic format is
@samp{mailserver:[@var{mailbox}/@var{subject}[/@var{body}]}.  Thus,
@samp{mailserver:foo@@bar.com/wibble/flibble} will compose a message to
foo@@bar.com with @var{subject} as the subject and @var{body} already in
the body of the email.  Note that both the subject and the body are
@dfn{hex}ed, but the subject cannot contain newlines.

@node news/nntp/snews, rlogin/telnet/tn3270, mailserver, Supported URLs
@section news/nntp/snews
@cindex news
@cindex nntp
@cindex snews
@cindex news @sc{url}s
@vindex url-news-use-article-mode
@vindex url-news-server
@vindex url-default-ports
If the @sc{url} doesn't specify a host, then the host in
@code{url-news-server} will be used, and unless the @sc{url} has a port
the news port as defined in @code{url-default-ports} (119) will be used.
The username and password specified in the @sc{url} will be used if
present.  The @sc{url} may contain a message-id, in which case that
article is displayed; it may contain a newsgroup in which case Gnus is
used to display the newsgroup; or it may by empty in which case Gnus is
called with no arguments.  Emacs/W3 requires Gnus v5.x or Red, Quassia
or Pterodactyl Gnus, @xref{Top, , ,gnus, Gnus}.  The variable
@code{url-news-use-article-mode} controls the displaying of news
articles; if non-@code{nil} then articles are displayed in Gnus article
mode, otherwise they are turned into @sc{html} and rendered by Emacs/W3.

An @sc{nntp url} is the same as a news @sc{url}, except that the
@sc{url} may specify an article by its number.

@node rlogin/telnet/tn3270, irc, news/nntp/snews, Supported URLs
@section rlogin/telnet/tn3270
@cindex rlogin
@cindex telnet
@cindex tn3270
@cindex rlogin @sc{url}s
@cindex telnet @sc{url}s
@cindex tn3270 @sc{url}s
To handle rlogin, telnet and tn3270 @sc{url}s, Emacs/W3 runs an
@code{rlogin}, @code{telnet} or @code{tn3270} session (the program names
and arguments are hardcoded) in a @code{terminal-emulator} buffer.
Well-known ports are used if the @sc{url} does not specify a port.


@node irc, data, rlogin/telnet/tn3270, Supported URLs
@section irc
@cindex @sc{irc}
@cindex @sc{irc url}s
@vindex url-irc-function
@dfn{Internet Relay Chat} (@sc{irc}) is handled by handing off the @sc{irc}
session to a function named in @code{url-irc-function}.  This function
must take five argumenst, @var{host}, @var{port}, @var{channel},
@var{user} and @var{password}.  The @var{channel} argument specifies the
channel to join immediately, this can be @code{nil}.  By default this is
@code{url-irc-zenirc} which processes the arguments and lets
@code{zenirc} handle the session.

@node data, gopher, irc, Supported URLs
@cindex data @sc{url}s
@section data

Data @sc{url}s contain @sc{mime} data in the @sc{url} itself, by default
the data is 8bit encoded @samp{text/plain}, but the @sc{url} can specify either
or both the content-type and the encoding.  Emacs/W3 will parse the
@sc{url}'s data as @sc{mime} and display it appropriately.  @xref{MIME Support}.

@node gopher, finger, data, Supported URLs
@section gopher
@cindex gopher
@cindex gopher @sc{url}s
@vindex url-gopher-labels
@vindex url-gopher-icons
@vindex url-gopher-to-mime
@vindex url-use-hypertext-gopher
@dfn{Gopher} (Go for) was in someways the precurser to the world wide
web and is becoming rarer as the web becomes more powerful.
Nevertheless, there are still many gopher sites around and Emacs/W3
supports this protocol (of course).  The variable
@code{url-gopher-labels} maps gopher types to something else (gdj: ?)
for displaying the gopher menus.  @code{url-gopher-icons} maps gopher
types to pictures.  @code{url-gopher-to-mime} maps gopher types to
@sc{mime} types.  If @code{url-use-hypertext-gopher} is non-@code{nil},
then gopher pages will be turned into @sc{html} for Emacs/W3 to parse
and display normally, otherwise Emacs/W3 will let @samp{gopher.el}
handle all gopher requests which will lose gopher+ support and inlined
searching.  This is @code{t} by default.

@node finger,  netrek, gopher, Supported URLs
@section finger
@cindex finger
@cindex finger @sc{url}s
Finger @sc{url}s will finger a given user at a given host, or @samp{localhost}
if no host is specified, processing the results to create an @sc{html}
page for Emacs/W3 to display.

@node netrek, , finger, Supported URLs
@section netrek
This is unsupported at present.


@node MIME Support, Security, Supported URLs, Top
@chapter MIME Support
@sc{mime} is an emerging standard for multimedia mail.  It offers a very
flexible typing mechanism.  The type of a file or message is specified
in two parts, separated by a '/'.  The first part is the general
category of the data (text, application, image, etc.).  The second part
is the specific type of data (postscript, png, jpeg, etc.).  So
@samp{text/html} specifies an @sc{html} document, whereas
@samp{image/x-xwindowdump} specifies an image of an Xwindow taken with
the @file{xwd} program.


This typing allows much more flexibility in naming files.  @sc{http}/1.0
servers can now send back content-type headers in response to a request,
and not have the client second-guess it based on file extensions.  @sc{html}
files can now be named @file{something.png} (not a great idea, but
possible).

@menu
* Adding MIME types based on file extensions::  How to map file
                                                extensions onto MIME
                                                types (e.g., @samp{.png ->
                                                image/png)}.
* Specifying Viewers::          How to specify external and internal viewers
                        for files that Emacs/W3 cannot handle natively.
@end menu

@node Adding MIME types based on file extensions, Specifying Viewers, MIME Support, MIME Support
@section Adding MIME types based on file extensions

@vindex mm-mime-extensions
For some protocols however, it is still necessary to guess the content
of a file based on the file extension.  This type of guess-work should
only be needed when accessing files via @sc{ftp}, local file access, or old
@sc{http}/0.9 servers.

Instead of specifying how to view things twice, once based on
content-type and once based on the file extension, it is easier to map
file extensions to MIME content-types.  The variable that controls this
is @code{mm-mime-extensions}.

This variable is an assoc list of file extensions and the corresponding
MIME content-type.  A sample entry looks like: @samp{(".movie"
. "video/x-sgi-movie")} This makes all files that end in @file{.movie}
(@file{foo.movie} and @file{bar.movie}) be interpreted as SGI animation
files.  If a content-type is defined for the document, then this is
over-ridden.  Regular expressions can @b{NOT} be used.

@cindex mime-types file
@findex mm-parse-mimetypes
Both Mosaic and the NCSA @sc{http} daemon rely on a separate file for mapping
file extensions to MIME types.  Instead of having the users of Emacs/W3
duplicate this in lisp, this file can be parsed using the
@code{url-parse-mimetypes} function.  This function is called each time
w3 is loaded.  It tries to locate mimetype files in several places. If
the environment variable @code{MIMETYPES} is nonempty, then this is
assumed to specify a UNIX-like path of mimetype files (this is a colon
separated string of pathnames).  If the @code{MIMETYPES} environment
variable is empty, then Emacs/W3 looks for these files:

@enumerate
@item
@file{~/.mime-types}
@item
@file{/etc/mime-types}
@item
@file{/usr/etc/mime-types}
@item
@file{/usr/local/etc/mime-types}
@item
@file{/usr/local/www/conf/mime-types}
@end enumerate

Each line contains information for one @sc{http} type.  These types resemble
MIME types.  To add new ones, use subtypes beginning with x-, such as
application/x-myprogram.  Lines beginning with # are comment lines, and
suitably ignored.  Each line consists of:

type/subtype ext1 ext2 ...  ext@var{n}

type/subtype is the MIME-like type of the document. ext* is any number
of space-separated filename extensions which correspond to the MIME
type.

@node Specifying Viewers,  , Adding MIME types based on file extensions, MIME Support
@section Specifying Viewers

Not all files look as they should when parsed as an @sc{html} document
(whitespace is stripped, paragraphs are reformatted, and lots of little
changes that make the document look unrecognizable).  Files may be
passed to external programs or Emacs Lisp functions to be viewed.

Not all files can be viewed accurately from within an Emacs session (PNG
files for example, or audio files).  For this reason, the user can
specify file "viewers" based on MIME content-types.  This is done with
a standard mailcap file.  @xref{Mailcap Files}.

@findex mm-add-mailcap-entry
As an alternative, the function @code{mm-add-mailcap-entry} can also be
used from an appropriate hook.  @xref{Hooks}.  This functions takes three
arguments, the major type ("@i{image}"), the minor type ("@i{png}"), and
an assoc list of information about the viewer.  Please see the @sc{url}
documentation for more specific information on what this assoc list
should look like.

@node Security, Cookies, MIME Support, Top
@chapter Security
@cindex Security
@cindex Paranoia
There are an increasing number of ways to authenticate a user to a web
service.  Emacs/W3 tries to support as many as possible.  Emacs/W3
currently supports:

@table @b
@item Basic Authentication
@cindex Security, Basic
@cindex HTTP/1.0 Authentication
@cindex Authentication, Basic
The weakest authentication available, not recommended if serious
security is necessary.  This is simply a string that looks like
@samp{user:password} that has been Base64 encoded, as defined in RFC
1421.
@item Digest Authentication
@cindex Security, Digest
@cindex HTTP/1.0 Authentication
@cindex Authentication, Digest
Jeffery L. Hostetler, John Franks, Philip Hallam-Baker, Ari Luotonen,
Eric W. Sink, and Lawrence C. Stewart have an internet draft for a new
authentication mechanism.  For the complete specification, please see
draft-ietf-http-digest-aa-01.txt in the nearest internet drafts
archive@footnote{One is ftp://ds.internic.net/internet-drafts}.
@item SSL Encryption
@cindex HTTP/1.0 Authentication
@cindex Secure Sockets Layer
@cindex SSL
@cindex Gag Puke Retch
@cindex Exportability
@cindex Export Restrictions
SSL is the @code{Secure Sockets Layer} interface.  Emacs/W3 supports
@sc{http} transfers over an SSL encrypted channel, if the appropriate
files have been installed.  @xref{Installing SSL}.
@end table

@section Privacy
@vindex url-privacy-level
Sometimes you don't want people to know who you are, or where you've
been.  @sc{http} is quite happy to tell everyone it meets who you are
and where you've come from.  @code{url-privacy-level} can be used to set
how much information is given, it can be a list of the following symbols

@table @samp
@item email
Do not send email address.  This just sets
@code{url-personal-mail-address} to @code{nil}.
@item os
Do not send operating system
@item lastloc
Do not send the last location
@item agent
Do not send the User-Agent string (for an alternative approach,
@pxref{Masquerading}).
@item cookie
Never accept cookies (@pxref{Cookies})
@end table

Alternatively @code{url-privacy-level} can be a single symbol,
@table @samp
@item none
Send all information.
@item low
Don't send the last location.  Equivalent to @code{(lastloc)}
@item high
Don't send the email address or last location.  Equivalent to
@code{(email lastloc)}
@item paranoid
Don't send anything.  Equivalent to @code{(email os lastloc agent cookie)}
@end table

If you change @code{url-privacy-level} then you should also call
@code{url-setup-privacy-info} to make sure that the changes propogate.

@node Cookies, Non-Unix Operating Systems, Security, Top
@chapter Cookies
@cindex Cookies

@sc{http} is a stateless protocol which means that the server sees every
request for pages independently with no idea of how it relates to any
other request.  Therefore the server has no idea whether or not you've
seen a page before, or whether you've registered (if that's an option).
Cookies@footnote{In computer terms a @dfn{cookie} is data that a
program holds but which has no meaning in itself.  Cookies are not
processed by the program (indeed the program may not even know
what data they hold or what format it's in) but is passed to libraries or
servers which do understand it.} are used to add state to @sc{http}
sessions.  Cookies are defined in @sc{rfc2109}.

@vindex url-cookie-file
Cookies are saved in the file specified in @code{url-cookie-file}, which
is @code{@var{w3-configuration-directory}/cookies} by default.  Note
that this file should probably not be world writable, and possibly not
even world readable.

@vindex url-cookie-untrusted-urls
@vindex url-cookie-trusted-urls
@vindex url-cookie-confirmation
Some people see cookies as an invasion of privacy while others see them
as a product of badly designed websites and buggy servers.  Emacs/W3
lets you unconditionally reject all cookies by adding @code{cookie} to
@code{url-privacy-level} or setting it to @code{paranoid}
(@pxref{Security}) but for those who want finer control over what to
accept and reject, Emacs/W3 offers @code{url-cookie-trusted-urls} and
@code{url-cookie-untrusted-urls} which are lists of regular expressions
that match @sc{url}s from which cookies should be accepted and rejected
respectively.  If a @sc{url} matches patterns in both of these, then
Emacs/W3 decides whether to accept or not based on the most specific
match (the most specific match being the shortest match).
@c gdj1: This doesn't seem right.
Note that Emacs/W3 only considers the first match for each variable, so
the regular expressions should be in increasing order of generality.

For even more control over which cookies are accepted, you can set
@code{url-cookie-confirmation} to non-@code{nil}, in which case every
time a cookie is offered Emacs/W3 will ask if you want to accept it.
This only applies to cookies that would otherwise be accepted, Emacs/W3
will still reject cookies from @sc{url}s matched in
@code{url-cookie-untrusted-urls}.

@node Non-Unix Operating Systems, Speech Integration, Cookies, Top
@chapter Non-Unix Operating Systems
@cindex Non-Unix Operating Systems

@menu
* VMS::                         The wonderful world of VAX|AXP-VMS!
* OS/2::                        The next-best thing to Unix.
* MS-DOS::                      The wonderful world of MS-DOG!
* Windows::                     Windows NT, Chicago/Windows 95.
@end menu

@node VMS, OS/2, Non-Unix Operating Systems, Non-Unix Operating Systems
@section VMS
@cindex VAX-VMS
@cindex AXP-VMS
@cindex Digital VMS
@cindex VMS

:: WORK :: VMS Specific instriuctions

@node OS/2, MS-DOS, VMS, Non-Unix Operating Systems
@section OS/2
@cindex OS/2
@cindex Warp

:: WORK :: OS/2 Specific instructions

@node MS-DOS, Windows, OS/2, Non-Unix Operating Systems
@section MS-DOS
@cindex MS-DOS
@cindex Microsloth
@cindex DOS
@cindex MS-DOG

:: WORK :: DOS Specific instructions

@node Windows,  , MS-DOS, Non-Unix Operating Systems
@section Windows
@cindex Windows (32-Bit)
@cindex 32-Bit Windows
@cindex Microsloth
@cindex Windows '95

:: WORK :: 32bit Windows Specific instructions

@node Speech Integration, Advanced Features, Non-Unix Operating Systems, Top
@chapter Speech Integration

:: WORK :: Emacspeak integration

@node Advanced Features, More Help, Speech Integration, Top
@chapter Advanced Features

@menu
* Disk Caching::                Improving performance by using a local disk cache
* Printing::                    Emacs/W3 can print @sc{html} by various methods.
* Interfacing to Mail/News::    How to make VM understand hypertext links
* Debugging HTML::              How to make Emacs/W3 display warnings about invalid
                                @sc{html}/@sc{html}+ constructs.
* Hooks::                       Various hooks to use throughout Emacs/W3
* Other Variables::             Miscellaneous variables that control the real
                                guts of Emacs/W3.
@end menu

@node Disk Caching, Printing, Advanced Features, Advanced Features
@section Disk Caching
@cindex Caching
@cindex Persistent Cache
@cindex Disk Cache

A cache stores the information on a page on the local machine.  When
requesting a page that is in the cache, Emacs/W3 can retrieve the page
from the cache more quickly than retrieving the page again from its
location out on the network.  With a well-populated cache, browsing the
web is dramatically faster.

The first time a page is requested, Emacs/W3 retrieves the page from the
network.  When requesting a page that is in the cache, Emacs/W3 checks
to see if the page has changed since it was last retrieved from the
remote machine.  If it has not changed, the local copy is used, saving
the transmission of the file over the network.

@vindex url-automatic-caching
@cindex Turning on caching
@cindex Cleaning the cache
@cindex Clearing the cache
@cindex Cache cleaning
@cindex Limiting the size of the cache
To turn on disk caching, set the variable @code{url-automatic-caching}
to non-@code{nil}, or choose the 'Caching' menu item (under `Options').
That is all there is to it.  Running the @code{clean-cache} shell script
fist is recommended, to allow for future cleaning of the cache.  This
shell script will remove all files that have not been accessed since it
was last run.  To keep the cache pared down, it is recommended that this
script be run from @i{at} or @i{cron} (see the manual pages for
crontab(5) or at(1) for more information)


@cindex Relying on cache
@cindex Cache only mode
@cindex Standalone mode
@cindex Browsing with no network connection
@cindex Netless browsing
@vindex url-standalone-mode
With a large cache of documents on the local disk, it can be very handy
when traveling, or any other time the network connection is not active
(a laptop with a dial-on-demand PPP connection, etc).  Emacs/W3 can rely
solely on its cache, and avoid checking to see if the page has changed
on the remote server.  In the case of a dial-on-demand PPP connection,
this will keep the phone line free as long as possible, only bringing up
the PPP connection when asking for a page that is not located in the
cache.  This is very useful for demonstrations as well.  To turn this
feature on, set the variable @code{url-standalone-mode} to
non-@code{nil}, or choose the `Use Cache Only' menu item (under
`Options')

@findex url-cache-expired
@vindex url-cache-ignored-protocols
@vindex url-cache-directory
@vindex url-cache-creation-function
@code{url-cache-expired} decides whether or not a cache entry has
expired.  It is a function that take two times as it parameters and
returns non-@code{nil} if the second time is ``too old'' when compared
with the first time.  @code{url-cache-ignored-protocols} is a list of
protocols that will never be cached, this is @code{'("www" "about"
"https" "mailto")} by default. @code{url-cache-directory} sets the
directory to store the cache files,
@file{"@var{w3-configuration-directory}cache/"} by default.
@code{url-cache-creation-function} sets the type of cache to use, it is
a function that takes a @sc{url} as an argument and returns the absolute
pathname of the cache-file corresponding to that @sc{url}.  You may
write your own function or use one of the two ready built functions, 
@code{url-cache-create-filename-using-md5} and
@code{url-cache-create-filename-human-readable}.  The advantage of
@code{url-cache-create-filename-using-md5} is that there are very few
cache collisions but is only ``suitably fast'' if you're not using
XEmacs.  @code{url-cache-create-filename-human-readable} will give a
filename more obviously connected to the @sc{url}, but it is more likely
to conflict with other files.

@node Printing, Interfacing to Mail/News, Disk Caching, Advanced Features

@section Printing
@cindex Printing
@cindex LaTeX
@cindex Postscript

If you want to print an @sc{html} document, then Emacs/W3 needs to
convert it into something that can be printed.  You can choose from

@table @asis
@item @sc{html} source
This will simply print the raw @sc{html} source code using
@code{lpr-buffer}.  An appropriate <base> tag is inserted at the
beginning of the document. @c gdj1: really?

@item Formatted text
This will print the rendered document using @code{lpr-buffer}; so the
conversion is handled by Emacs.  This will print plain ASCII.

@item Postscript
@vindex w3-postscript-print-function
This will call the function in @code{w3-postscript-print-function},
which is @code{ps-print-buffer-with-faces} by default.  This just tells
Emacs to generate postscript as best it can.

@item LaTeX
Emacs/W3 can generate a LaTeX equivalent of the @sc{html} document.

@vindex w3-print-command
@code{w3-print-command} contains a command string to print @file{dvi}
files.  It is @samp{lpr -h -d} by default.


There are several variables controlling what the final LaTeX document looks like.

:: WORK :: Document the new LaTeX backend


@table @code
@item w3-latex-use-latex2e
@vindex w3-latex-use-latex2e
If non-@code{nil}, configures the LaTeX engine to use the LaTeX2e
syntax.  A @code{nil} value indicates that LaTeX 2.0.9 compabibility
will be used instead.
@item w3-latex-docstyle
@vindex w3-latex-docstyle
The document style to use when printing or mailing converted @sc{html} files
in LaTeX.
@item w3-latex-packages
@vindex w3-latex-packages
List of LaTeX packages to include.  Currently this is only used if 
@code{w3-latex-use-latex2e} is non-@code{nil}.
@item w3-latex-use-maketitle
@vindex w3-latex-use-maketitle
If non-@code{nil}, the LaTeX engine will use real LaTeX title pages for
document titles.
@item w3-latex-print-links
@vindex w3-latex-print-links
If non-@code{nil}, prints the @sc{url}s of hypertext links as endnotes at the
end of the document.  If set to @code{footnote}, prints the @sc{url}'s as
footnotes on each page.
@end table
@end table


@node Interfacing to Mail/News, Debugging HTML, Printing, Advanced Features
@section Interfacing to Mail/News
@cindex Interfacing to Mail/News
@cindex VM
@cindex Using Emacs/W3 with VM
@cindex GNUS
@cindex Using Emacs/W3 with Gnus
@cindex RMAIL
@cindex Using Emacs/W3 with RMAIL

More and more people are including @sc{url}s in their signatures, and within
the body of mail messages.  It can get quite tedious to type these into
the minibuffer to follow one. 

@vindex browse-url-browser-function
With the latest versions of VM (the 5.9x series of betas) and Gnus
(5.x), @sc{url}s are automatically highlighted, and can be followed with the
mouse or the return key.  How the @sc{url}s are viewed is determined by the
variable @code{browse-url-browser-function}, and it should be set to the
symbol @code{browse-url-w3}.

To access @sc{url}s from within RMAIL, the following hook should do the
trick.
@example
(add-hook 'rmail-mode-hook
	  (function
	   (lambda ()
	     (define-key rmail-mode-map [mouse-2] 'w3-maybe-follow-link-mouse)
	     (define-key rmail-mode-map "\r"      'w3-maybe-follow-link))))
@end example

@node Debugging HTML, Hooks, Interfacing to Mail/News, Advanced Features
@section Debugging HTML
@cindex Debugging
@cindex Invalid HTML
@cindex Bad HTML
@vindex w3-debug-buffer
@vindex w3-debug-html
@vindex w3-display-errors-hook
@vindex w3-html-errors-font-lock-keywords
For those people that are adventurous, or are just as anal as I am about
people writing valid @sc{html}, set the variable @code{w3-debug-html} to
@code{t} and see what happens.  Alternatively, you can set it to
@code{style} to warn about stylistic issues as well.  The debugging
information will be written to the buffer named by
@code{w3-debug-buffer}, @file{*HTML Debug*} by default.  To control
font-lock highlighting in the @sc{html} error buffer, use
@code{w3-html-errors-font-lock-keywords}.  After Emacs/W3 has displayed
@sc{html} errors for a page, it runs @code{w3-display-errors-hook}.


If a Emacs/W3 thinks it has encountered invalid @sc{html}, then a debugging
message is displayed.

:: WORK :: Need to list the different values w3-debug-html can have, and@*
:: WORK :: what they do ::

gdj1: Does this refer to the macro?  And if so, why?

@node Hooks, Other Variables, Debugging HTML, Advanced Features
@section Hooks
@cindex Hooks

These are the various hooks that can be used to customize some of
Emacs/W3's behavior.  They are arranged in the order in which they would
happen when retrieving a document.  These are all 'normal hooks' in
standard Emacs-terminology, meaning they are functions (or lists of
functions) that are called consecutively.

@table @code
@vindex w3-load-hook
@item w3-load-hook
These hooks are run the first time a @sc{url} is fetched.  All the
Emacs/W3 variables are initialized before this hook is run.
@item w3-mode-hook
These hooks are run after a buffer has been parsed and displayed, but
before any inlined images are downloaded and converted.
@item w3-source-file-hook
These hooks are run after displaying a document's source.
@end table

@node Other Variables,  , Hooks, Advanced Features
@section Miscellaneous variables

There are lots of variables that control the real nitty-gritty of Emacs/W3
that the beginning user probably shouldn't mess with.  Here they are.

@table @code
@item url-bad-port-list
@vindex url-bad-port-list
List of ports to warn the user about connecting to.  Defaults to just
the mail, @sc{nntp} and chargen ports so a malicious @sc{html} author
cannot spoof mail or news to other people.
@item url-confirmation-func
@vindex url-confirmation-func
What function to use for asking yes or no functions.  Possible values
are @code{'yes-or-no-p} or @code{'y-or-n-p}, or any function that takes
a single argument (the prompt), and returns @code{t} only if a positive
answer is gotten.  Defaults to @code{'yes-or-no-p}.

@item url-passwd-entry-func
@vindex url-passwd-entry-func
This is a symbol indicating which function to call to read in a
password.  If this variable is @code{nil} at startup, it is initialized
depending on whether @dfn{EFS} or @dfn{ange-ftp} is being used.  This
function should accept the prompt string as its first argument, and the
default value as its second argument.

@item url-max-password-attempts
@vindex url-max-password-attempts
When a protected document is requested, Emacs/W3 will prompt for a
password.  @code{url-max-password-attempts} controls how many attempts
should be allowed, it is 5 by default.

@item w3-reuse-buffers
@vindex w3-reuse-buffers
Determines what happens when @code{w3-fetch} is called on a document
that has already been loaded into another buffer.  Possible values are:
@code{nil}, @code{yes}, and @code{no}.  @code{nil} will ask the user if
Emacs/W3 should reuse the buffer (this is the default value).  A value of
@code{yes} means assume the user wants to always reuse the buffer.  A
value of @code{no} means assume the user always wants to re-fetch the
document.

@item url-show-status
@vindex url-show-status
Whether to show progress messages in the minibuffer.
@code{url-show-status} controls if a running total of the
number of bytes transferred is displayed.  This Can cause a large
performance hit if using a remote X display over a slow link, or a
terminal with a slow modem.

@item mm-content-transfer-encodings
@vindex mm-content-transfer-encodings
An assoc list of @var{Content-Transfer-Encodings} or
@var{Content-Encodings} and the appropriate decoding algorithms for each.
If the @code{cdr} of a node is a list, then this specifies the decoder is
an external program, with the program as the first item in the list, and
the rest of the list specifying arguments to be passed on the command line.
If using an external decoder, it must accept its input from @code{stdin}
and send its output to @code{stdout}.

If the @code{cdr} of a node is a symbol whose function definition is
non-@code{nil}, then that encoding can be handled internally.  The function
is called with 2 arguments, buffer positions bounding the region to be
decoded.  The function should completely replace that region with the
unencoded information.

Currently supported transfer encodings are: base64, x-gzip, 7bit, 8bit,
binary, x-compress, x-hqx, and quoted-printable.

@item url-uncompressor-alist
@vindex url-uncompressor-alist
An assoc list of file extensions and the appropriate uncompression
programs for each.  This is used to build the Accept-encoding header for
@sc{http}/1.0 requests.

@item w3-do-scripting
@vindex w3-do-scripting
If this is non-@code{nil} then Emacs/W3 will do clien-side scripting.
This is @code{nil} by default.

@item url-external-retrieval-program, url-external-retrieval-args
@vindex url-external-retrieval-program
@vindex url-external-retrieval-args
@c gdj1: Find out what this means.
@code{url-external-retrieval-program} names the external program that is
run to retrieve @sc{url}s.  It is @file{www} by default.
@code{url-external-retrieval-args} specifies the arguments that will be
passed to it, @samp{("-source")} by default.

@item w3-netscape-compatible-comments
@vindex w3-netscape-compatible-comments
Not everyone uses proper @sc{html} comments.  To allow for the presence
of lesser browsers, Emacs/W3 will honour the incorrect netscape-style
comments (@samp{<! >}) if @code{w3-netscape-compatible-comments} is
non-@code{nil}.  This is @code{t} by default, but it shouldn't need to
be.

@item font-blink-interval
@vindex font-blink-interval
This controls how often blinks occur for text inside @samp{<blink>}
tags.  It is 0.5 seconds by default.

@item url-inhibit-mime-parsing
@vindex url-inhibit-mime-parsing
This controls whether to parse @sc{mime} headers in a message.  If it is
@code{nil} then the headers are parsed and deleted.

@item url-mime-language-string
@vindex url-mime-language-string
This is used to set the contents of the @samp{Accept-language:} field in
@sc{http/1.0} requests.  If it is @code{nil} then the field isn't added
and the server's default language version is retrieved, if it is
@code{*} then the first available langauge version is retrieved.  If it
is a string, then it should be the desired language.
@c gdj1: find out how http/1.0 differs from http/1.1 here.

@item url-multiple-p
@vindex url-multiple-p
If this is non-@code{nil} then multiple queries are possible through
@file{ *URL-<i>*} buffers.

@item url-personal-mail-address
@vindex url-personal-mail-address
@code{url-personal-mail-address} contains your full email address.  This
is sent in the @sc{from} field in an @sc{http/1.0} request, but
@ref{Security} for how to prevent this.  If @code{nil} (the default),
then it will be set to @code{user-mail-address} if non-@code{nil}, else
it will be @code{(user-real-login-name)} at @code{(system-name)}.

@item url-temporary-directory, w3-temporary-directory
@vindex url-temporary-directory
@vindex w3-temporary-directory
@code{url-temporary-directory} and @code{w3-temporary-directory} control
where temporary files are placed.  If @samp{TMPDIR} is set then they
default to that, otherwise @file{/tmp}.

@item w3-documentation-root
@vindex w3-documentation-root
This specifies the location of the Emacs/W3 documentation, it
@emph{must} end in a slash.

@item w3-popup-menu-on-mouse-3
@vindex w3-popup-menu-on-mouse-3
If you like context-sensitive menus then you're bound to like
@code{w3-popup-menu-on-mouse-3}.  If non-@code{nil} (the default) then
Emacs/W3 will bind mouse-3 to provide context-sensitive menus.  This
might not work at the moment.  If @code{w3-popup-menu-on-mouse-3} is
@code{nil}, then Emacs/W3 will not change the binding of mouse-3.

@item w3-track-mouse
@vindex w3-track-mouse
If @code{w3-track-mouse} is non-@code{nil} (the default) then Emacs/W3
will display the @sc{url} under the mouse in the echo-area.

@item w3-use-menus
@vindex w3-use-menus
If @code{w3-use-menus} is @code{nil} then Emacs/W3 will not provide a
menu interface.  If it is @samp{1}, then Emacs/W3 will add a @samp{W3}
item to the Emacs menubar.  If it is a list then Emacs/W3 will add its
own menubar.  The following symbols may appear in the list to control
what Emacs/W3 puts in its menubar.
@table @code
@item file
A list of file related commands
@item edit
Various standard editing commands (copy/paste)
@item view
Controlling various things about the document view
@item go
Navigation control
@item bookmark
Bookmark / hotlist control
@item options
Various options
@item buffers
The standard buffers menu
@item emacs
A toggle button to switch back to normal emacs menus
@item style
Control style information and who gets to set what
@item search
Various search engines
@item help
The help menu
@item nil
This may appear once in the list.  All menus after this will be
displayed flush right.
@end table

@end table

@node More Help, Future Directions, Advanced Features, Top
@chapter More Help
@cindex Relevant Newsgroups
@cindex Newsgroups
@cindex Support
For more help on Emacs/W3, please send me mail
(@i{wmperry+w3@@cs.indiana.edu}).  Several discussion lists have also been
created for Emacs/W3.  To subscribe, send mail to
@i{majordomo@@indiana.edu}, with the body of the message 'subscribe
@var{listname} @var{<email addres>}'.  All other mail should go to
@i{<listname>@@indiana.edu}.


@itemize @bullet
@item
w3-announce -- this list is for anyone interested in Emacs/W3, and
should in general only be used by me.  The gnu.emacs.sources newsgroup
and a few other mailing lists are included on this.  Please only use
this list for major package releases related to Emacs/W3.
(@i{www-announce@@w3.org} is included on this list).
@item
w3-beta -- this list is for beta testers of Emacs/W3.  These brave souls test
out not-quite stable code.
@item
w3-dev -- a list consisting of myself and a few other people who are
interested in the internals of Emacs/W3, and doing active development work.
Pretty dead right now, but I hope it will grow.
@end itemize

For help on the World Wide Web in general, please refer to the
comp.infosystems.www.* newsgroups.  There are also several discussion
lists concerning the Web.  Send mail to @i{<listname>-request@@w3.org}
with a subject line of 'subscribe <listname>'.  All mail should go to
@i{<listname>@@w3.org}.  Administrative mail should go to
@i{www-admin@@w3.org}.  The lists are:


@itemize @bullet
@item
www-talk -- for general discussion of the World Wide Web, where its
going, new features, etc.  All the major developers are subscribed to
this list.
@item
www-announce -- for announcements concerning the World Wide Web.  Server
changes, new servers, new software, etc.
@end itemize

As a last resort, mail me.  I'll try to answer as quickly as I can.

@node Future Directions, Reporting Bugs, More Help, Top
@chapter Future Directions
Changes are constantly being made to the Emacs browser (hopefully all
for the better).  This is a list of the things that are being worked on
right now.

BUGS (4.0):
@itemize @minus
@item
need to support HTTP/0.9 (http://c2.com:8080) responses
@item
/etc/mailcap cannot overide builtin mm-mime-data stuff?
@item
try to protect people from using '~' in file URLs
@item
keystrokes entered while in w3-pause self-insert under XEmacs --- the
loop around dispatch-event needs to be smarter about what it
swallows.
@item
border-color can have multiple color specifications, but we
currently choke with 'args out of range' when we see this.
@item
widget appears to be stealing button3 to mean 'activate' --- this is
bogus!  We lose all context-sensitive menus because of this.
@item
We still seem to be growing the line size under Emacs 19.x/20.x
@item
It would be really nice if w3 buffers were put into w3-mode as soon
as they were created. Then if the rendering craps out somehow then
the buffer could be browsed such as it was. Ideally, links and
widgets would be functional.
@item
document how to translate Netscape foo.pac files to emacs lisp
@item
Should we stop using reporter.el?
@end itemize

BUGS (4.1):
@itemize @minus
@item
background colors are not heeded on table rows (<tr>).  Same
properties on individual cells or the table as a whole work fine.
@item
<br> in <dd> hosed --- margins in general tend to be too big sometimes.
@item
client side imagemaps have to be in the same buffer (actually in the
smae buffer, _BEFORE_ the usemap directive on an image) --- fix to be
able to use imagemaps in different files, any position, etc, etc.
@end itemize

FEATURES (4.1)
@itemize @minus
@item
cache a formatted version of documents, with enough info to recreate
the widgets in them.
@item
w3-preview-region command
@item
LDAP support (XEmacs)
@item
New proxy type for sending requests via mail to a mail->web->mail gateway.
@item
Emacspeak Interaction

@itemize @bullet
@item
some way of specifying in a stylesheet whether certain text is
inaudible.  use the 'inaudible text property for this.
@item
Full Aural-CSS support
@end itemize

@item
more sophisticated filling algorithm. I'm not sure exactly what
would be sufficient but breaking lines after punctuation  seems like
it would solve most of the problem.
@item
When fetching images for viewing (not inlining), W3 should at least
have an option of displaying it inline, ala Netscape.
@item
Widget library merging

@itemize @bullet
@item
Write a font selection widget
@item
Write a voice selection widget
@item
Write a mailcap entry widget
@end itemize

@item
Custom library merging
@bullet{Add custom support for MM}
@item
Hotlist handling

@itemize @bullet
@item
Abstract out current support
@item
Do something similar to GNUS 'backends' to provide easy way to add new
bookmark formats, etc.
@end itemize

@item
Write a new major mode for handling CSS style sheets
@end itemize

FEATURES (5.0)

@itemize @minus
@item
Emacspeak Integration

@itemize @bullet
@item
Need option to turn off table rendering and print it out as a
table that is viewable with emacspeak-table-ui.el
@end itemize

@item
Write a text/xml parser
@item
Completely rewrite display code again

@itemize @bullet
@item
Abstract everything out to follow parse->flow objects->render model
@item
Base all stylesheet stuff off of DSSSL
@item
CSS2
@item
New rendering backends

@itemize @minus
@item
Native postscript output
@item
LaTeX upgrade
@item
TeXinfo
@end itemize
@end itemize

@item
Display code

@itemize @bullet
@item
implement <spacer> from netscape 3.0b5
@item
reimplement w3-show-headers
@item
Handle math environment using the calc library
@item
Better integration with the parser
@end itemize
@end itemize


@node Reporting Bugs, Dealing with Firewalls, Future Directions, Top
@appendix Reporting Bugs
@cindex Reporting Bugs
@cindex Bugs
@cindex Contacting the author

If any bugs are discovered in Emacs/W3, please report them to the
mailing list @t{w3-beta@@xemacs.org} --- this is where the brave souls
who beta test the latest versions of Emacs/W3 reside, and are generally
very responsive to bug reports.
@kindex w
@findex w3-submit-bug
Please make sure to use the bug submission feature of Emacs/W3, so that
all relevant information will be sent along with your bug report.  By
default this is bound to the `@key{w}' key when in an Emacs/W3 buffer,
or you can use @key{M-x w3-submit-bug} from anywhere within Emacs.

For problems that are causing emacs to signal and error, please send a
backtrace.  You can get a backtrace by @kbd{M-x setvariable RET
debug-on-error RET t RET}, and then reproduce the error.

If the problem is visual, please capture a copy of the output and mail
it along with the bug report (preferably as a MIME attachment, but
anything will do).  You can use the @code{xwd} program under X-windows
for this, or @key{Alt-PrintScreen} under Windows 95/NT.  Sorry, but I
don't remember what the magic incarnation is for doing a screen dump
under NeXTstep or OS/2.

If the problem is actually causing Emacs to crash, then you will need to
also mail the maintainers of the various Emacs distributions with the
bug.  Please use the @t{gnu.emacs.bug} newgroup for reporting bugs with
GNU Emacs 19, and @t{comp.emacs.xemacs} for reporting bugs with XEmacs
19 or XEmacs 20.  I am actively involved with the beta testing of the
latest versions of both branches of Emacs, and if I can reproduce the
problem, I will do my best to see it gets fixed in the next release.

It is also important to always maintain as much context as possible in
your responses.  I get so much email from my various Emacs-activities
and work, that I cannot remember everything.  If you send a bug report,
and I send you a reply, and you reply with 'no that didn't work', then
odds are I will have no clue what didn't work, much less what that was
trying to fix in the first place.  It will be much quicker and less
painful if I don't have to waste a round-trip email exchange saying
'what are you talking about'.

@node Dealing with Firewalls, Proxy Gateways, Reporting Bugs, Top
@appendix Dealing with Firewalls
By default, Emacs can support standard @sc{tcp}/@sc{ip} network
connections on almost all the platforms it runs on (Unix, @sc{vms},
Windows, etc).  However, there are several situations where it is not
sufficient.

@table @b
@cindex Firewalls
@item Firewalls
It is becoming more and more common to be behind a firewall or some
other system that restricts your outbound network activity, especially
if you are like me and away from the wonderful world of academia.
Emacs/W3 has several different methods to get around firewalls (not to
worry though --- none of them should get you in trouble with the local
@sc{mis} department.)

@item Emacs cannot resolve hostnames.
@cindex Faulty hostname resolvers
@cindex Broken SunOS libc
@cindex Hostname resolution
This happens quite often on SunOS workstations and some ULTRIX machines.
Some C libraries do not include the hostname resolver routines in their
static libraries.  If Emacs was linked statically, and was not linked
with the resolver libraries, it wil not be able to get to any machines
off the local network.  This is characterized by being able to reach
someplace with a raw ip number, but not its hostname
(@url{http://129.79.254.191/} works, but
@url{http://www.cs.indiana.edu/} doesn't).

The best solution for this problem is to recompile Emacs, making sure to
either link dynamically (if available on your operating system), or
include the @file{-lresolv}.

@cindex url-gateway-broken-resolution
If you do not have the disk space or the appropriate permissions to
recompile Emacs, another alternative is using the @file{nslookup}
program to do hostname resolution.  To turn this on, set the variable
@code{url-gateway-broken-resolution} in your @file{~/.emacs} file.  This
runs the program specified by @code{url-gateway-nslookup-program} (by
default "@code{nslookup}" to do hostname resolution.  This program should
expect a single argument on the command line --- the hostname to resolve,
and should produce output similar to the standard Unix @file{nslookup}
program:

@example
Name: www.cs.indiana.ed
Address: 129.79.254.191
@end example

@cindex @sc{term}
@item Using @sc{term} (or @sc{term}-like) Networking Software
@sc{term} @footnote{@sc{term} is a user-level protocol for emulating
@sc{ip} over a serial line.  More information is available at
@url{ftp://sunsite.unc.edu/pub/Linux/apps/comm/term}} for slip-like
access to the internet.

@sc{note}: XEmacs and Emacs 19.22 or later have patches to enable native
@sc{term} networking.  To enable it, @code{#define TERM} in the
appropriate s/*.h file for the operating system, then change the
@code{SYSTEM_LIBS} definition to include the @file{termnet} library that
comes with the latest versions of @sc{term}.

If you run into any problems with the native @sc{term} networking
support in Emacs or XEmacs, please let @t{wmperry+w3@@cs.indiana.edu} know,
as he is responsible for the original support.
@end table

@vindex url-gateway-local-host-regexp
Emacs/W3 has support for using the gateway mechanism for certain
domains, and directly connecting to others.  The variable
@code{url-gateway-local-host-regexp} controls this behaviour.  This is a
regular expression @footnote{Please see the full Emacs distribution for
a description of regular expressions} that matches local hosts that do
not require the use of a gateway.  If @code{nil}, then all connections
are made through the gateway.

@vindex url-gateway-method
Emacs/W3 supports several methods of getting around gateways.  The
variable @code{url-gateway-method} controls which of these methods is
used.  This variable can have several values (use these as symbol names,
not strings), ie: @samp{(setq url-gateway-method 'telnet)}.  Possible
values are:

@table @dfn
@item telnet
Use this method if you must first telnet and log into a gateway host,
and then run telnet from that host to connect to outside machines.

@vindex url-gateway-telnet-host
@vindex url-gateway-telnet-parameters
@vindex url-gateway-telnet-password-prompt
@vindex url-gateway-telnet-user-name
@vindex url-gateway-prompt-pattern
@vindex url-gateway-telnet-login-prompt
@vindex url-gateway-telnet-password
@table @code
@item url-gateway-telnet-host
The gateway host to telnet to.  Once logged in there, you then telnet
out to the hosts you want to connect to.
@item url-gateway-telnet-parameters
This should be a list of parameters to pass to the @file{telnet} program.
@item url-gateway-telnet-password-prompt
This is a regular expression that matches the password prompt when
logging in.
@item url-gateway-telnet-login-prompt
This is a regular expression that matches the username prompt when
logging in.
@item url-gateway-telnet-user-name
The username to log in with.
@item url-gateway-telnet-password
This is the password to send when logging in.
@item url-gateway-prompt-pattern
This is a regular expression that matches the shell prompt.
@end table


@item rlogin
This method is identical to the @code{telnet} method, but uses
@file{rlogin} to log into the remote machine without having to send the
username and password over the wire every time.

@vindex url-gateway-rlogin-host
@vindex url-gateway-rlogin-parameters
@vindex url-gateway-rlogin-user-name
@vindex url-gateway-prompt-pattern
@table @code
@item url-gateway-rlogin-host
Host to @samp{rlogin} to before telnetting out.
@item url-gateway-rlogin-parameters
Parametres to pass to @samp{rsh}.
@item url-gateway-rlogin-user-name
User name to use when logging in to the gateway.
@item url-gateway-prompt-pattern
This is a regular expression that matches the shell prompt.
@end table

@item tcp
Masanobu UMEDA (@i{umerin@@mse.kyutech.ac.jp}) has written a very small
application that you can run in a subprocess to do the network
connections.

@item @sc{socks}
Use if the firewall has a @sc{socks} gateway running on it.  @sc{socks}
v5 protocol is defined in @sc{rfc1928}.

@vindex socks-password
@vindex socks-username
@vindex socks-timeout
@vindex socks-server
@vindex socks-server-aliases
@vindex socks-network-aliases
@vindex socks-redirection-rules
@vindex socks-nslookup-program
@table @code
@item socks-password
If this is @code{nil} then you will be asked for the passward, otherwise
it will be used as the password for authenticating you to the @sc{socks}
server.

@item socks-username
This is the username to use when authenticating yourself to the
@sc{socks} server.  By default this is your login name

@item socks-timeout
This controls how long, in seconds, Emacs/W3 will wait for responses from the
@sc{socks} server; it is 5 by default.

@item socks-server
Thiss the default server, it take the form (@samp{"Default server"}
@var{server} @var{port} @var{version}) where @var{version} can be either
4 or 5.

@item socks-server-aliases
This a list of server aliases.  It is a list of aliases of the form
@var{(alias hostname port version)}.

@item socks-network-aliases
This a list of network aliases.  Each entry in the list takes the form
@var{(alias (network))} where @var{alias} is a string that names the
@var{network}.  The networks can contain a pair (not a dotted pair) of
@sc{ip} addresses which specify a range of @sc{ip} addresses, an @sc{ip}
address and a netmask, a domain name or a unique hostname or @sc{ip}
address.

@item socks-redirection-rules
This a list of redirection rules.  Each rule take the form
@var{(Destination network Connection type)} where @var{Destination
network} is a network alias from @code{socks-network-aliases} and
@var{Connection type} can be @code{nil} in which case a direct
connection is used, or it can be an alias from
@code{socks-server-aliases} in which case that server is used as a
proxy.

@item socks-nslookup-program
This the @samp{nslookup} program.  It is @samp{nslookup} by default.
@end table


@c @item ssl
@c This probably shouldn't be documented

@item native
This means that Emacs/W3 should use the builtin networking code of
Emacs.  This should be used only if there is no firewall, or the Emacs
source has already been hacked to get around the firewall.
@end table

Emacs/W3 should now be able to get outside the local network.  If none
of this makes sense, its probably my fault.  Please check with the
network administrators to see if they have a program that does most of
this already, since somebody somewhere at the company has probably been
through something similar to this before, and would be much more
helpful/knowledgeable about the local setup than I would be.  But feel
free to mail me as a last resort.

@node Proxy Gateways, Installing SSL, Dealing with Firewalls, Top
@appendix Proxy Gateways
@vindex url-proxy-services
@cindex Proxy Servers
@cindex Proxies
@cindex Proxies, environment variables
@cindex HTTP Proxy

In late January 1993, Kevin Altis and Lou Montulli proposed and
implemented a new proxy service.  This service requires the use of
environment variables to specify a gateway server/port # to send
protocol requests to.  Each protocol (@sc{http}, @sc{wais}, gopher,
@sc{ftp}, etc.) can have a different gateway server.  The environment
variables are @code{PROTOCOL}_proxy, where @code{PROTOCOL} is one of the
supported network protocols (gopher, file, @sc{http}, @sc{ftp}, etc.)

@cindex No Proxy
@cindex Proxies, exclusion lists
@vindex NO_PROXY
For companies with internal intranets, it will usually be helpful to
define a list of hosts that should be contacted directly, @b{not} sent
through the proxy.  The @code{NO_PROXY} environment variable controls
what hosts are able to be contacted directly.  This should be a comma
separated list of hostnames, domain names, or a mixture of both.
Asterisks can be used as a wildcard.  For example:

@example
NO_PROXY=*.aventail.com,home.com,*.seanet.com
@end example

tells Emacs/W3 to contact all machines in the @b{aventail.com} and
@b{seanet.com} domains directly, as well as the machine named
@b{home.com}.

@vindex url-proxy-services
@cindex Proxies, setting from lisp
For those adventurous souls who enjoy writing regular expressions, all
the proxy settings can be manipulated from Emacs-Lisp.  The variable
@code{url-proxy-services} controls this.  This is an assoc list, keyed
on the protocol type (@sc{http}, gopher, etc) in all lowercase.  The
@code{cdr} of each entry should be the @sc{address} of the proxy server
to contact, followed by ":" and the port number to use. In the case of
the special "no_proxy" entry, it should be a regular expression that
matches any hostnames that should be contacted directly.

@example
(setq url-proxy-services
       '(("http"     . "proxy.aventail.com:80")
         ("no_proxy" . "^.*\\(aventail\\|seanet\\)\.com")))
@end example

@node Installing SSL, Mailcap Files, Proxy Gateways, Top
@appendix Installing SSL
@cindex HTTP/1.0 Authentication
@cindex Secure Sockets Layer
@cindex SSL
@cindex Gag Puke Retch
@cindex Exportability
@cindex Export Restrictions
In order to use SSL in Emacs/W3, an implementation of SSL is necessary.
Emacs/W3 is configued to work out of the box with SSLeay 0.6.6 or later.
For best results, you should apply a patch that makes the SSLeay client
much quieter about what it reports.

You can download SSLeay from
@url{ftp://ftp.psy.uq.oz.au/pub/Crypto/SSL/}

The following variables control how the external program is invoked.

@table @code
@item ssl-program-name
@vindex ssl-program-name
The name of the program to run, as a string.

@example
(setq ssl-program-name "s_client")
@end example

@item ssl-program-arguments
@vindex ssl-program-arguments
This should be used if your SSL program needs command line switches to
specify any behaviour (certificate file locations, etc).  This is a list
of strings and symbols.

The special symbols 'host and 'port may be used in the list of arguments
and will be replaced with the hostname and service/port that will be
connected to.

@example
(setq ssl-program-arguments '("-host" host
                              "-port" service
                              "-verify" "4"
                              "-CApath /usr/local/ssl/certs"))
@end example
@end table
The default is ("-host" host "-port" service "-verify"
@var{ssl-certificate-verification-policy} -CApath @var{ssl-certificate-directory}).

@vindex ssl-certificate-directory
@code{ssl-certificate-directory} is the directory in which @sc{ca}
certificates are stored.  It is
@code{@var{w3-configuration-directory}/cert} by default.

@vindex ssl-rehash-program-name
@code{ssl-rehash-program-name} is the program that is run after adding a
certificate to the @code{ssl-certificate-directory} directory.  It is
run with the directory name as an argument and defaults to @code{c_rehash}.

@vindex ssl-view-certificate-program-name
@vindex ssl-view-certificate-program-arguments
@code{ssl-view-certificate-program-name} names the program that can
produce a human-readable view of a certificate.  It is @code{x509} by
default and is called with the arguments listed in
@code{ssl-view-certificate-program-arguments} which is @code{("text"
"-inform" "DER")} by default.

@vindex ssl-certificate-directory-style
@code{ssl-certificate-directory-style} specifies the type of certificate
database to use.  It's default (and at the moment, only possible value)
is @code{ssleay} which specifies a directory or pem encoded certificates
with hash symlinks.

@vindex ssl-certificate-verification-policy
You can decide how high up the chain of certificates should
be verified by setting @code{ssl-certificate-verification-policy}.  Possible
values are
@table @asis
@item 0
No verification
@item 1
Verification required
@item 3
Reject connection if verification fails
@item 5
SSL_VERIFY_CLIENT_ONCE
@end table
The default is 0

@node Mailcap Files, Temporary, Installing SSL, Top
@appendix Mailcap Files
NCSA Mosaic and almost all other WWW browsers rely on a separate file
for mapping MIME types to external viewing programs.  This takes some of
the burden off of browser developers, so each browser does not have to
support all image formats, or postscript, etc.  Instead of having the
users of Emacs/W3 duplicate this in lisp, this file can be parsed using
the @code{mm-parse-mailcaps} function.  This function is called each
time Emacs/W3 is loaded.  It tries to locate mimetype files in several
places. If the environment variable @code{MAILCAPS} is nonempty, then
this is assumed to specify a UNIX-like path of mimetype files (this is a
colon separated string of pathnames).  If the @code{MAILCAPS}
environment variable is empty, then Emacs/W3 looks for these
files:

@enumerate
@item
@file{~/.mailcap}
@item
@file{/etc/mailcap}
@item
@file{/usr/etc/mailcap}
@item
@file{/usr/local/etc/mailcap}
@end enumerate

This format of this file is specified in RFC 1343, but a brief synopsis
follows (this is taken verbatim from sections of RFC 1343).

Each mailcap file consists of a set of entries that describe the proper
handling of one media type at the local site.  For example, one line
might tell how to display a message in Group III fax format.  A mailcap
file consists of a sequence of such individual entries, separated by
newlines (according to the operating system's newline
conventions). Blank lines and lines that start with the "#" character
(ASCII 35) are considered comments, and are ignored.  Long entries may
be continued on multiple lines if each non-terminal line ends with a
backslash character ('\', ASCII 92), in which case the multiple lines
are to be treated as a single mailcap entry.  Note that for such
"continued" lines, the backslash must be the last character on the line
to be continued.

Each mailcap entry consists of a number of fields, separated by
semi-colons.  The first two fields are required, and must occur in the
specified order.  The remaining fields are optional, and may appear in
any order.

The first field is the content-type, which indicates the type of data
this mailcap entry describes how to handle.  It is to be matched against
the type/subtype specification in the "Content-Type" header field of an
Internet mail message.  If the subtype is specified as "*", it is
intended to match all subtypes of the named content-type.

The second field, view-command, is a specification of how the message or
body part can be viewed at the local site.  Although the syntax of this
field is fully specified, the semantics of program execution are
necessarily somewhat operating system dependent.

The optional fields, which may be given in any order, are as follows:
@itemize @bullet
@item
The "compose" field may be used to specify a program that can be used to
compose a new body or body part in the given format.  Its intended use
is to support mail composing agents that support the composition of
multiple types of mail using external composing agents.  As with the
view- command, the semantics of program execution are operating system
dependent.  The result of the composing program may be data that is not
yet suitable for mail transport---that is, a Content-Transfer-Encoding
may need to be applied to the data.
@item
The "composetyped" field is similar to the "compose" field, but is to be
used when the composing program needs to specify the Content-type header
field to be applied to the composed data.  The "compose" field is
simpler, and is preferred for use with existing (non-mail-oriented)
programs for composing data in a given format.  The "composetyped" field
is necessary when the Content-type information must include auxilliary
parameters, and the composition program must then know enough about mail
formats to produce output that includes the mail type
information.
@item
The "edit" field may be used to specify a program that can be used to
edit a body or body part in the given format.  In many cases, it may be
identical in content to the "compose" field, and shares the
operating-system dependent semantics for program execution.
@item
The "print" field may be used to specify a program that can be used to
print a message or body part in the given format.  As with the
view-command, the semantics of program execution are operating system
dependent.
@item
The "test" field may be used to test some external condition (e.g.  the
machine architecture, or the window system in use) to determine whether
or not the mailcap line applies.  It specifies a program to be run to
test some condition.  The semantics of execution and of the value
returned by the test program are operating system dependent.  If the
test fails, a subsequent mailcap entry should be sought.  Multiple test
fields are not permitted---since a test can call a program, it can
already be arbitrarily complex.
@item
The "needsterminal" field indicates that the view-command must be run on
an interactive terminal.  This is needed to inform window-oriented user
agents that an interactive terminal is needed.  (The decision is not
left exclusively to the view-command because in some circumstances it
may not be possible for such programs to tell whether or not they are on
interactive terminals.)  The needsterminal command should be assumed to
apply to the compose and edit commands, too, if they exist.  Note that
this is NOT a test---it is a requirement for the environment in which
the program will be executed, and should typically cause the creation of
a terminal window when not executed on either a real terminal or a
terminal window.
@item
The "copiousoutput" field indicates that the output from the
view-command will be an extended stream of output, and is to be
interpreted as advice to the UA (User Agent mail- reading program) that
the output should be either paged or made scrollable. Note that it is
probably a mistake if needsterminal and copiousoutput are both
specified.
@item
The "description" field simply provides a textual description,
optionally quoted, that describes the type of data, to be used
optionally by mail readers that wish to describe the data before
offering to display it.
@item
The "x11-bitmap" field names a file, in X11 bitmap (xbm) format, which
points to an appropriate icon to be used to visually denote the presence
of this kind of data.
@item
Any other fields beginning with "x-" may be included for local or
mailer-specific extensions of this format.  Implementations should
simply ignore all such unrecognized fields to permit such extensions,
some of which might be standardized in a future version of this
document.
@end itemize

@node Temporary, General Index, Mailcap Files, Top
@comment  node-name,  next,  previous,  upGeneral Index

@c @appendix Temporary

@c @subsection base64
@c @itemize @code
@c 
@c gdj1: What is DSSSL?
@c 
@c @vindex font-maximum-slippage
@c @item font-maximum-slippage
@c This specifies how much a font can vary from the desired size.  It is a
@c string and the default value is @samp{1pt}.

@c @vindex font-family-mappings
@c @item font-family-mappings
@c This is an alist that tells Emacs/W3 what fonts correspond to the
@c @sc{html} font families.  The format is @code{(@var{html_family}
@c . (@var{fonts}))}.
@c 
@c @end itemize

@node General Index, Key Index, Temporary, Top
@appendix General Index
@printindex fn
@node Key Index,  , General Index, Top
@appendix Key Index
@printindex ky
@contents
@bye
