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Fast and Easy XHTML

by Shirley E. Kaiser, M.A., SKDesigns

Published December, 2001. Updated March, 2006. Copyright © 2001-2021, Shirley E. Kaiser, M.A., SKDesigns. All rights reserved. Published at with permission.

Wondering how to turn your HTML markup into XHTML? Here are a few quick tips to teach you the very basics, a sample XHTML document, and resources for more information.

If you already know HTML, I suspect you can learn how to implement these markup changes within a couple of hours. If you just dig in and give it a try, I think you'll be pleasantly surprised to see that it's easier than you may have thought.

Ready to give it a try? Let's go....

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The Basics

  1. All your markup needs to be in lowercase. For example, instead of <P></P> it needs to be <p></p> for XHTML.
  2. Every tag must have a corresponding ending tag, such as <p></p> and <li></li>. Some tags don't have a corresponding ending tag, such as <br>, <hr>, and others. Those tags, to be backward compatible will look like this instead:

    <br />
    <hr />

    (Below is an XHTML document sample that shows more of these.)
  3. Every attribute value must be in double quotes, such as:
    <img src="image.gif" height="150" width="40" alt="funny face" />

    Notice that since the <img> tag doesn't have a corresponding ending tag that it also is closed with the extra space and slash, too.
  4. Nesting must be correct (and symmetrical). HTML also requires correct nesting, but it wasn't always as problematic in browsers. XHTML requires it done properly, though. For example, this is incorrect:

    This is correct:
  5. An ampersand (&) within an attribute value must use its character entity reference. For example, a URL like this:

    <a href="

    must instead be:

    <a href="
  6. Your markup must be well-formed. If you've already been writing good markup that validates with W3C, it's no big deal. If not, it's a good time to clean up your markup.


In addition to the above is a new DTD, too. The sample below is for XHTML 1.0 transitional.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<html xmlns="">

The first line, beginning with <?xml version= ..., is the xml prolog, and it's recommended but not required. Note that using the xml prolog will trigger IE6 Quirks Mode, so you might want to leave it out or learn more about it before deciding. The xml prolog tells the browser that your document is based upon a DTD using XML, and that it's using a standard character encoding.

The second line, beginning with <!DOCTYPE ....>, will look more familiar to you, this time representing XHTML 1.0 transitional.

Then, the last line beginning with <html xmlns=" ....> replaces the <html> element, telling the browser the language and the namespace.

Below is a sample XHTML document. Note that all the markup is in lowercase, there are quotes around the attribute values, the new endings for the tags that don't have corresponding ending tags, and it is all well formed.

A Sample XHTML Document

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

<html xmlns="">

Nifty New XHTML document</title>

<meta name="description" content="This is the coolest XHTML document on the Internet." />

<link rel="stylesheet" type="text/css" href="stylesheet.css" />



Content here.</p>
<p>Content here.</p>

List item one</li>
   <li>List item two</li>


<img src="image.gif" height="150" width="40" alt="funny face" />


<table class="data">
Green eggs</td><td>Ham</td></tr>

<form method="get" action="foo">

<select name="">
<option value="all">All Products
<option value="books">Books</option>

<input type="text" name="keyword" size="10"

<input type="submit" name="Search" value="Go!" />




 Book cover: XML, HTML, XHTML Magic, by Molly Holzschlag  To learn lots more about XHTML, check out's XHTML section for annotated links to W3C recommendations, articles and tips, sites devoted to XHTML, and more.

Also highly recommended is Molly Holzschlag's book, XML, HTML, XHTML Magic published by New Riders.

This tutorial was originally published December 09, 2001 at Brainstorms and Raves.

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