If you need to edit some of the advanced preferences of Firefox, and you need a neater way to get that done, gui:config is right for you.
This extension of Firefox will give you a lot of the “about:config” preferences, in an easy to navigate menu box. It displays the options, included in the current version, using checkboxes, dropdown lists and textboxes.
If you want to check out all the advanced settings that gui:config makes available to you, Lifehacker has done a nice gallery of each tab you see in the screenshot above.
I would consider this extension well worth trying out, at least. The add-on, gui:config is a must have for anybody who likes to tweak and customize their browsing experience. You can find out more about the development at: http://guiconfig.freedig.org/.