Have you ever typed
about:config into Firefox's address bar? If you do, you'll get back a huge array of files that you can modify to configure and customize your Firefox installation. Some people like to play with these. I don't like to, and that's why I'm a big fan of
FireTune. FireTune is a free, downloadable utility that automates the process of improving your Firefox setup. The application simply asks you to specify a few questions about your computer and connection speed, then automatically configures Firefox for optimal performance?in seconds. FireTune is newly updated for Firefox version 3. Here is a screenshot-driven guide to it.