Quite a lot of Firefox users know this but there might still be a couple of people out there who do not know of this little tweak.
To back up your Bookmarks,
-Click on Bookmarks
-Click on Organize Bookmarks
-Go to Import and Backup
-Select Export HTML…
-Save it anywhere as a html file and you are done.
-Go to Documents and Settings > USERNAME > Application Data > Mozilla > Firefox > Profiles > cxhmjww8.default (this name is random)
-Backup the following files
+signons2.txt (if you’re using FF 2.0+)
+signons3.txt (if you’re using FF 3.0+)
+signons.sqlite (if you’re using FF 3.5+)
These files contain data regarding your saved passwords. After a reinstall, overwrite these files back to this folder.