Many Firefox settings can only be changed in the about:config dialog that appears when you type the phrase in the Firefox address bar. The settings in there however have rather cryptic names and it can sometimes be quite hard to figure out what they do, actually not that hard because every setting is explained on the Mozilla website. Still, it takes some time to look them up.
Configuration Mania is a Firefox add-on that displays many of those “deeper” settings in a menu that resembles the Firefox options menu. Users can access five main tabs, like Browser or Security, which lead to several subtabs that provide access to the settings.
Let me give you an example that helped me actually. Clicking on the Browser tab opens a menu with several like User Agent, Location Bar and Download. A click on Download revealed the option to disable the alert that you receive when a download finishes. I would have a hard time finding that option in the about:config settings.

Users who would like to keep the alert can chance the interval in that it is shown and even increase or decrease the speed of the animation. You can find dozens of such helpful settings in Configuration Mania.
Related posts:
- Advanced Firefox Configuration Tips
- Mozilla Firefox About Protocol Links
- Apple and AT&T Will Learn that User Agents are no good for access control
- Firefox 3.1 Improvements
- Moving The Firefox Disk Cache To Another Drive
- Firefox About:Support Helps In Troubleshooting Browser Problems
- Tweak Firefox with about:config
- Check if you Firefox speed tweaks are still active

Good tip, valuable tool.
Seems a nice extension.
Martin,does it have the option that the data downloaded in the download manager should always be shown in kb.
As i use dialup i dont like to see data downloaded in mb.
Mutant no it does not have this option.
you can get more control over downloads with Download Statusbar
https://addons.mozilla.org/en-US/firefox/addon/26
Check out the fun with Firefox.. and a new use too
http://www.techtola.com/2008/03/fun-with-firefox-browser-inside-browser.html
Slowed my browser down dramatically with bad “Paint & Rendering” settings. I set all of the settings to the listed defaults and the browser is now chugging along versus its previous peppy pace. Uninstalled the extension, restarted FIREFOX, and the browser is still chugging along and is dead slow at window controls and tab switching. I strongly recommend you to not install this extension as it does not “revert” changed settings back to their originals.
Found a webpage with fixes for the “Paint & Rendering” slowdown from “Configuration Mania”. This webpage below explains what these settings are and what they recommend for your browser to work correctly again.
Hacking Page Rendering
http://www.extremetech.com/article2/0,1697,1854509,00.asp
user_pref(“content.notify.ontimer”, true);
user_pref(“content.interrupt.parsing”, true);
user_pref(“content.notify.interval”, 100);
user_pref(“content.notify.threshold”, 100000);
user_pref(“content.notify.backoffcount”, 200);
user_pref(“content.max.tokenizing.time”, 3000000);
user_pref(“content.maxtextrun”, 8191);