Quite good idea: show questionable HTML constructs with the help of CSS. Someone should create a CSS file of these tips
Library of CSS stylesheets and HTML templates for formatting academic publications for print and the web. Currently, support the: ACM SIG Proceedings, ACM SIGCHI Conference Papers, ACM SIGCHI Extended Abstracts, IEEE Conference Proceedings.
Nice introductionary text book.
Compiler for the Sass language, a superset of CSS3 that adds programming capabilities and some other syntactic sugar.