Introduction to XHTML
http://www.xguru.com/tutorial/news.asp?id=9

Duffy, Scott
XGuru
2003

Abstract:

Most people have heard of HTML - the language of the web. Far fewer have heard of XHTML. Believe it or not, HTML is dead and XHTML is here to take its place. This article goes through XHTML in technical detail, and points out the key differences between it and traditional HTML.