If you haven’t made the jump yet, there are a few files you may want to make sure you back up before going from Firefox 2 to Firefox 3. The first would be your password files. These files are located in your profile folder.
Backup the Firefox files called:
Copy and past them into the place you want to back them up to, and you are done. To restore them, make sure you don’t have Firefox running and then go into your current profile folder and copy and move them in. They should replace the ones in there currently.
Now to backup your Firefox 2 boomarks, dive back into your profile folder and look for a file called “bookmarkbackups”. Double-click that folder, and there you have some of your saved bookmarks that you thought you had lost waiting for you to restore them.
To restore your bookmarks in Firefox 3, go to Bookmarks and then Organize Bookmarks. In the Library, click on Import and Backup and click on “Import HTML”. The on screen wizard should walk you through the rest of the steps.