To backup your firefox browser settings you must locate and save your profile. You will find your profile stored on your hard drive at these locations on:

Windows Vista/XP/2000:
C:\Documents and Settings\Dave\Application Data\Mozilla\Firefox\Profiles

You can copy the location above, paste it into your ‘My Computer’ address bar and change the username Dave to your own windows user.

Windows 98/Me:
C:\WINDOWS\Application Data\Mozilla\Firefox\Profiles\

Once your inside the Profiles directory then you need to copy the profile file to your backup device, it will be named something like ‘xn1q3oa2.default’.