Using Firebug to edit CSS, how do I save/export changes made to the CSS?

TOOLS: Firefox, Firebug

MAJOR UPDATE: If you know of a way to lock the forward/back/refresh on a FireFox tab, please let me know. Otherwise, I've given up on using FireBug/FireDiff as an IDE for CSS, it's nice, but lol... press backspace at the wrong time and ALL your work is gone... funny. So, really like the browser highlighting to CSS/HTML in Firebug. Know any good CSS editors that do this? Really had hope FireBug would work, but for now only see it as being good for ad-hoc inspection and test; meaning using it for what it's made for.

UPDATES:

@Lèse majesté: Just as an update, "Web Developer add-on" does let you edit CSS, but it does not let you edit/save CSS changes made by Firebug. Meaning you use Firebug to ID and maybe test changes, but it does not let you save the changes from Firebug. Here's a "how to" covering how to use them together: FF + FB + WD

@Lèse majesté: Still playing around with FireDiff. It works okay, found one bug already (although I'm just working around it), and there's no "how to" I've been able to find, so I'm just trying every feature and clicking around... (for example, to export a diff you must be over the last item in the list, right click, and select as "Save Diff". The ".diff" is just a text file, no idea why at this point the ext is .diff.