A New Riders book by Charles Wyke-Smith
Good XHTML markup makes your content portable, accessible and future-proof. Creating XHTML-compliant pages simply requires following a few simple rules. Also, XHTML code can be easily validated online so you can be sure it is correctly written.
Here are the key requirements for successful validation of your XHTML code.
You can find more CSS related links at the Stylin' with CSS site.