W3School Tutorial

1. http://www.w3schools.com/xhtml/xhtml_intro.asp
2. This tutorial is geared toward the beginner level.
3. I would recommend this site to others because it explains the nature and uses of XHTML in a clear way that anyone can understand.
4. An important difference between XHTML and HTML 4.01 is that all XHTML characters must be in lowercase letters.

WebHeadStart Tutorial

1. http://www.webheadstart.org/xhtml/
2. This tutorial is geared toward both the beginner and intermediate levels.
3. I would recommend this site because it color codes the attributes used in XHTML, making the coding process much easier to understand.
4. The XML declaration is optional in XHTML.