about:config is the bane for Firefox users looking into getting deeper with configuring their browsers. This is great, since you have direct access to FF’s registry, without having to open another application. Just enter about:config into the URL field and you’re in. Thing is, you have to be pretty sure what you’re doing or you might end up breaking your installation or at least messing it up. Or perhaps you’re not adventurous enough to sift through thousands of lines of registry options.
Configuration Mania will definitely change the way we approach the about:config settings in Firefox. For one, it gives you a GUI and classifies the different configuration settings into sections from the browser, to security and network, the UI and debugging. That rids the guesswork on preference names and what they do. Plus, each feature has some explanation to the customizable values.