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.
With this extension you can view CSS properties of related page elements. Very handy, when You got large CSS file with styles overlapping each other, to analyze why something is not displayed in the way You wanted.
FireBug is a new tool for Firefox that aids with debugging Javascript, DHTML, and Ajax. It is like a combination of the Javascript Console, DOM Inspector, and a command line Javascript interpreter.
Firediff is a Firebug extension that tracks changes to a pages DOM and CSS.
