Are you a FireFox user?
If YES:
You may have installed countless add-on in Firefox to enhance your using experience, but if you want to get the most out of Firefox, you really have to hack your way into the about:config.
The about:config page contains most (if not, all) of Firefox configuration options. It is so far the most effective, and the most powerful way to tweak and enhance your Firefox performance. Here are 28 of the popular tweaks.
Accessing your about:config page
In your Firefox, type about:config in the address bar.