Firefinder is an extension to Firebug (in Firefox) and offers the functionality to, in a quick way, find HTML elements matching chosen CSS selector(s) or XPath expression. It allows you to instantly test your CSS selectors in the page while seeing the content at the same time, and matching elements will be highlighted.
CSS Coverage is an extension for Firebug which allows you to scan multiple pages of your site to see which CSS rules are actually used in your site. This extension requires Firebug.
Firediff is a Firebug extension that tracks changes to a pages DOM and CSS.
die extensions für die extension