User Guide

102 Chapter 7 Using Web Development Languages
What is XHTML?
XHTML (Extensible Hypertext Markup Language) is a reformulation of HTML as an
XML language. It is almost identical to HTML 4.01, but it is more strict and clean.
Using XHTML lets you reap the benefits of XML, while ensuring the backward and
future compatibility of your web documents. Following are some specific reasons for
using XHTML:
• It is designed to replace HTML. If you want your website to be a visible part of the
Internet in the future (and for it to be rendered properly), it is a sound investment
to begin coding in XHTML now.
• It is designed to be operable across devices, not just on PCs.
• XHTML is an XML language, so it offers the potential for extensibility. It also lets
you view, edit, and validate XHTML documents with standard XML tools.
• XHTML documents can use applications such as scripts and applets that rely on
the HTML Document Object Model or the XML Document Object Model.
• It requires quality code. This reduces the discrepancies between how different
user agents such as web browsers render a web document, because most of these
discrepancies are caused by incorrect or poorly formatted code.
XHTML works on HTML 4-compliant user agents and XML user agents, so you can
switch to XHTML without excluding anyone or waiting for XML-based browsers or
other user agents to become more prevalent. Because XHTML is so similar to HTML,
it is not difficult to switch from HTML to XHTML.
For more information, see the W3C specification for http://www.w3.org/TR/
xhtml11/XHTML 1.1 - Module-Based XHTML/a or http://www.w3c.org/TR/xhtml1/
XHTML 1.0/a. You can also search http://www.tutorialfind.comtutorialfind/a for
XHTML. Other good resources are Beginning XHTML, published 2000 by Wrox Press,
and http://www.w3schools.com/xhtml/default.aspWelcome to XHTML School/a.