# About using a Strict vs. Transitional DOCTYPE in HTML [edit]

This page discusses the difference in coding an XHTML file with a Strict DOCTYPE vs. a Transitional DOCTYPE.

## Introduction

If you are using XHTML to code a web page, you have a choice between using a Strict or a Transitional DOCTYPE. The Strict DOCTYPE means that your XHTML has to be completely standards-compliant. The Transitional DOCTYPE allows you to use some elements and attributes that were common in older HTML markup but that do not adhere to current standards.

The Reference section of this Help topic lists the elements and attributes that are allowed by the Transitional DOCTYPE but not by the Strict DOCTYPE for XHTML.

## How to Switch from HTML to XHTML

Go to Window -> Preferences -> Aptana -> Editors -> HTML. Change the default extension to ".xhtml". Apply the following "Initial HTML file Contents":

### XHTML 1.0 Strict

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    	<title>Untitled Document</title>
    </head>
    <body>

    </body>
    </html>

### XHTML 1.0 Transitional

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    	<title>Untitled Document</title>
    </head>
    <body>

    </body>
    </html>

### XHTML 1.1

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
    	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    	<title>Untitled Document</title>
    </head>
    <body>

    </body>
    </html>

## Reference

In general, most of the differences between using a Transitional and a Strict DOCTYPE have to do with the guideline that with a Strict DOCTYPE, all presentation information should be in CSS, not in the XHTML markup.

### Elements allowed with a Transitional but not Strict DOCTYPE

- `center`
- `font`
- `iframe`
- `strike`
- `u`

### Attributes allowed with a Transitional but not Strict DOCTYPE

- `align` - With Strict, `align` is still allowed on the following table elements:
  - `col`
  - `colgroup`
  - `tbody`
  - `td`
  - `tfoot`
  - `th`
  - `thead`
  - `tr`
- `alink`
- `background`
- `bgcolor`
- `border` - With Strict, `border` is still allowed on `table` element.
- `height` - With Strict, `height` is still allowed on `img` and `object`.
- `hspace`
- `language`
- `link`
- `name` - `name` is allowed in HTML 4.01 Strict, but not allowed on `form` and `img` in XHTML 1.0 Strict.
- `noshade`
- `nowrap`
- `target`
- `text`
- `vlink`
- `vspace`
- `width` - With Strict, `width` is allowed on `img`, `object`, `table`, `col`, and `colgroup`.

## Related Topics

- Creating a new HTML or CSS file

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