I am using the CSS Usage extension [1] for Firebug as a tool for this. Quote: How does it work? - Open up the first page of the site you want to check and pr

I am using the CSS Usage extension [1] for Firebug as a tool for this. Quote: How does it work? - Open up the first page of the site you want to check and press the "Scan" button in the "CSS Coverage" Firebug tab. - In case of a rich (Ajax or DHTML) site, open up as many divs/popups/tabs in the page as possible and press "Scan" again. - Visit other pages of your site and press "Scan" again. Each time you press "Scan", the CSS files that are included in the current page are shown with the number of times the rules has been found applied on your page before it. [1] https://addons.mozilla.org/en-us/firefox/addon/css-usage/ https://addons.mozilla.org/en-us/firefox/addon/css-usage/