css & xhtml

CSS
http://jigsaw.w3.org/css-validator/

xhtml
http://validator.w3.org/

http://www.freewebtemplates.com/template.php?id=52

http://www.nuviotemplates.com/

http://www.mitchinson.net/templates.php

http://cssmania.com/topics/web-tools/cms/ — very nice

http://www.squidoo.com/topics/education