Firediff is a Firefox extension designed to track changes in Firebug, made by Firebug and the software itself to CSS and the DOM.
This provides insight into the functionality of the software as well as provide a record of the changes that were required to debug and tweak the page's display.
It has the capability to view the exact DOM and CSS state at any given time. This allows the developer to visualize all of the changes that have been made to the page, be it the current page state or any change in between.

Requirements:
* Firefox
* Firebug

The license of this software is Free, you can free download and free use this browser plug-ins software.