Just a small link and example collection, hope it can help you!
You might want to visit one of the following pages:
Learn xHTML at the W3C
After that learn CSS at the W3C
Self-HTML
PHP-Net
Self-PHP
The HTML Hell Page on ESR's Homepage
Here are some easy-to-understand CSS Examples by me:
"Table" Layout without Tables ...
Centered Fixed Layout
Right aligning boxes which get to the next line if there isn't enough space
A nice Homepage to see a decent examples of using xhtml/css (decent in the way of, structured, and w3 valid):
Eric S. Raymond's Home Page
Maybe you can also learn from the code of this/my page itself, I don't know..