Backing up your information
http://support.mozilla.com/en-US/kb/Backing+up+your+information#Locate_your_profile_folderMozilla Firefox stores all your personal settings, such as bookmarks, passwords and extensions, in a profile folder, which is stored on your computer.
To back up your profile, restore it, or move it to a new location or computer, all you have to do is move or copy the profile folder.
In order to back up or restore your data, you need to know where Firefox stores the profile folder.
Each profile is stored on your hard drive in a profile folder.
* The following examples refer to a default profile for Windows Vista/XP/2000
C:\Documents and Settings\oldfogy\Application Data\Mozilla\Firefox\Profiles\
b30by31s.default
NB. These are random digits and will differ from person to person "
b30by31s" See option 2 below for restoring.
Backing up your profile folder in Firefox.
1. Locate your profile folder, as explained above.
2. Right-click & Hold down the Ctrl key while you click on your profile folder, and select Copy.
3. Right-click & Hold down the Ctrl key while you click the backup location (e.g. a Folder, USB-stick or a blank CD-RW disc), and select Paste item.
To restore a profile backup
1. If your existing profile folder and profile sub folder have the same name, simply replace the existing profile folder with the profile backup, then start Firefox.
2. If your backed-up profile sub folder has a different name (which it probably will) simply replace only the contents of the sub folder into the new existing sub folder.
Important: The profile sub folder name must match exactly for this to work, including the random string of 8 characters.
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edit. Text added and changed. (improved)