Looking for a CSS Tool

I saw something the other day and I can’t find it. It was a tool (a website I think) which would take a given page and identify which CSS rules were being used and which weren’t.

I’m not talking about Firebug, but something along the same concept. I didn’t bookmark it and I can’t find it in my history, so if anything comes to mind, please help me out…

http://www.sitepoint.com/dustmeselectors/

Should be what you are looking for