On the supposition that you're interested in the interaction of css *AND* browser, some info, data and or tools can be found:

• http://old.macedition.com/cb/resources/abridgedcsssupport.html (last modified 2004; a good backward look)
• http://www.quirksmode.org/dom/w3c_html.html DOM issues
• http://webmaster.info.aol.com/compatibility.html Somewhat dated
• http://www.netmechanic.com/products/browser-index.shtml Commercial tool
• See also http://en.wikipedia.org/wiki/Cross-browser NB: This article is, in my view, utterly wrong-headed in its assertion that cross-browser compatibility is less critical today than a decade ago (because newer browsers -- even IE -- are increasingly standards complaint).
• http://ipinfo.info/netrenderer/ limited to currently common versions of IE

And, though it scarcely needs saying and these are not, strictly speaking, responsive to your question, consider:

1. screen rez
2. screen size, and...
3. the user's connectivity (something like 50% of the US population *STILL* has no highspeed access) because it bears on whether your page will render for a member of your target audience before the individual gives up and browses elsewhere.

BTW, these are a merely few samples from a quick Google for " browser + compatibiltity" but there are other and better ones out there still. However, my usual references are at home whereas I'm on the road and yet another meeting calls. So take these with a grain of salt.