Best CSS Reference

Sitepoint has always been a decent online community and publishing company for web developers. They have articles written by top designers and coders and a number of really great reference books available for purchase. Recently, however, they added a new free reference section to their site that is incredibly useful. Currently only a CSS Reference is available but they are working on an HTML and Javascript section as well. There are many CSS references out there but this is by far the easiest to use. It is not written as a tutorial but rather a simple lookup and explanation (with samples) of every CSS property, rule, workaround, filter and hack. I few clicks and I found modifiers to properties that I had no idea existed.

Sitepoint CSS Reference