CSS-Discuss
- Wiki companion to the CssDiscussList mailing list. Includes tips and tricks and information on browser hacks, text sizing, and testing.
- http://css-discuss.incutio.com/

QuirksMode - CSS contents and browser compatibility
- Tests of CSS2 selectors, pseudoclasses and declarations, including compatibility information for Explorer, Mozilla, Safari, and Opera.
- http://www.quirksmode.org/index.html?/css/contents.html

Cascading Style Sheets Level 1 Browser Incompatibilities
- Teaches how to produce Web pages (formatted with Cascading Style Sheets Level 1) that display attractively on modern browsers and adequately on recent ones.
- http://www.ctlow.ca/CSS1/CSS1Incompatibility.html

Navigator / Explorer Comparison
- Comparison of how Netscape Navigator 4.x and Microsoft Internet Explorer for Windows render some examples of HTML and CSS.
- http://browsercomparison.esmartweb.com/

CSS Pointers Group: CSS Bugs and Workarounds
- A list of CSS bugs in various browsers for various platforms. Some include demonstrations and screenshots, and workarounds.
- http://css.nu/pointers/bugs.html

WestCiv - CSS1 and CSS2 Browser Support
- Groups properties by level of support. Contains guide, tutorials, and articles.
- http://www.westciv.com/style_master/academy/browser_support/

RichInStyle.com: CSS bug guide
- List of CSS1 and CSS2 bugs in other Internet Explorer, Netscape, Opera versions, and a bug-by-bug guide on how to avoid them.
- http://www.richinstyle.com/bugs/