Free xHTML Resources
A quick run down of what XHTML is, its benefits, how it can be used, and what it looks like.
This is designed to be a rough and ready tutorial to get the beginner up and running as quickly as possible.
XHTML tutorial at HTML Goodies.
This XHTML tutorial will show you how to code your pages using XHTML. (assumes a knowledge of html)
Fast and Easy XHTML
Short article about converting pages from html to xhtml. (PDF)
W3C XHTML 1.0 Recommendation
This specification defines XHTML 1.0, a reformulation of HTML 4 as an XML 1.0 application, and three DTDs corresponding to the ones defined by HTML 4.