That's because Firefox 3.6 added a helpful new about page for support and troubleshooting. Just type about:support in your Firefox address bar to give it a look. The new page separates a ton of useful troubleshooting information into sections, including Application Basics (name, version, profile directory, installed plug-ins, and build configuration, followed by all of your installed extensions, and then ending with your profile's modified preferences. Mozilla put this all together as a helpful tool for finding important information for users elbow deep in troubleshooting, but as Nirmal over at Life Rocks 2.0 points out, it also serves as a great shortcut for quickly backing up your Firefox profile.
Just click the Open Containing Folder (or Show in Finder in OS X) button to go straight to the profile folder for that Firefox installation. Once you're looking at it, backing up your profile is as simple as copying that folder. Windows users, you can also give previously mentioned MozBackup a look if you'd like help with the backup-and-restore process for everything from Firefox and Thunderbird to Songbird.
