Backup your firefox

Just check this tutorial to backup bookmarks:

https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Manual Backup :
 One way
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1. Click the menu button and then click Exit
2. Locate your profile folder, as explained above.
3. Go to one level above your profile's folder, i.e. to %APPDATA%\Mozilla\Firefox\Profiles\
4. Right-click on your profile folder (e.g. xxxxxxxx.default), and select Copy.
5. Right-click the backup location (e.g. a USB-stick or a blank CD-RW disc), and select Paste.

Another way
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Backing up Firefox and Thunderbird manually is as simple as copying their respective profile folders to another location. If you do that, you’ll have a full backup with all your setting and personal data saved.
An advantage of manual backup is that you don't need to have Firefox or Thunderbird functioning in order to restore your backup; it's just a case of copying the backup profiles. That's a good thing because the most common reason you want to restore is that your Firefox or Thunderbird installation is not working!
The hardest part is finding the profile folders. First up, they are not located where you would expect to find them. Secondly, they are located in different places for different versions of Windows. Thirdly, they may be assigned random file names that make them difficult to recognize.
On Windows 2000/XP machines the locations for your Firefox and Thunderbird profiles are respectively:

• C:\Documents and Settings\<Windows login/user name>\Application Data\Mozilla\Firefox\Profiles\<Profile name>\
• C:\Documents and Settings\<Windows login/user name>\Application Data\Thunderbird\Profiles\<Profile name>\

On Windows 9x/Me PCs they can usually be found at:

• C:\Windows\Application Data\Mozilla\Firefox\Profiles\<Profile name>\
• C:\Windows\Application Data\Thunderbird\Profiles\<Profile name>\ If you can't locate your profiles then check out this document for more information: http://kb.mozillazine.org/Profile_Folder#What_is_in_my_profile?
  On my XP laptop the profiles are:
• C:\Documents and Settings\Ian\Application Data\Mozilla\Firefox\Profiles\default.ebq
• C:\Documents and Settings\Ian\Application Data\Thunderbird\Profiles\25ve0lz5.default

To back these up I copy the profiles to an external USB drive. It's as simple as that. I do it manually but you could also use Windows Scheduler or a backup manager to do the job automatically. Make sure, though, that Firefox and Thunderbird are not running before you back up.