Step 1:
Close and reopen your Firefox browser application. In some cases the problem is a simple error in the program itself, which you can fix by closing and reopening Firefox.
Step 2:
Restart your computer if Step 1 doesn't work. This closes applications that may be interrupting Firefox's reset process.
Step 3:
Go to the Firefox Profile folder and open it if Steps 1 and 2 do not work. This should in the directory where you installed your Firefox application. Find and open the folder titled bookmarkbackups.
Step 4:
Locate the bookmarks.html files in the bookmarkbackups folder. Find which of the five files contains your bookmarks. You can see the bookmarks by opening each file in your Firefox web browser.
Step 5:
Open Firefox if it is not open already. Click on Bookmarks and then Organize Bookmarks. In this menu, go to File, then Import and finally select From File.
Step 6:
Find the bookmarks.html file that contains all the bookmarks in your bookmarkbackups folder. Select the bookmark file from the list.
Step 7:
Import the backup file into your Firefox bookmarks folder. You have recovered your lost Firefox bookmarks.
Hope it helps you. For more information http://www.iyogi.ca