Well I have the new Firefox 3 update and I'm new to tweaking Firefox so one of my friends told me that you can make Firefox even faster by giving it a few tweaks. I know that real speed depends on your internet connection, cpu, and etc. and these most of these tweaks just pre-fetch HTML markup and some compress JavaScript and other small files. But I did it anyway......So I went to about:config in Firefox 3 and set  “network.http.pipelining” to “true”, set “network.http.proxy.pipelining” to “true”, and “network.http.pipelining.maxrequests” to 25. They all work FINE and there is a slight speed INCREASE in Firefox 3 and then a few days ago I got an idea and made a new String called “nglayout.initialpaint.delay” and set it to zero, the PROBLEM then I realized the new String I made major problem is that websites with lots of pictures takes may refreshes in order to full load the page. So I thought i just delete String but in about:config I can't delete the String!!! Apparently I can delete booleans but I can't delete strings!! Can some tell me how to delete that String? Do I have to edit one of the files in Mozilla Folder, if so what is the file and where is it located?I don't think you can delete About:Config entries...

Right click the newly created entry and click Reset. Then Restart Firefox.Or create a new Profile...To Carbon Dudeoxide
Yeah, already tried, seems to work somewhat, but if anyone can figure out how to completely delete without requiring me to uninstall and then reinstall Firefox, would be much appreciated!

Trying Patios method now...All config entries are stored in prefs.js file, located in your profile.
In XP, your profile is located here: C:\Documents and Settings\\Application Data\Mozilla\Firefox\Profiles\
You can open, and edit prefs.js with Notepad.Thanks Broni, I just manually deleted that line in the prefs.js file USING Dreamweaver, and all seems to good now.Cool In the meantime grab MozBack....pretty handy tool for backing up Profiles, extensions, settings etc.

Works for ThunderBird as well ! !..or/and FEBE: https://addons.mozilla.org/en-US/firefox/addon/2109