Many people that i know have problems when installing new version of Mozzila Firefox over the old version, forget to backup their bookmarks, so here is one little program that i make with autoit. It reads your profiles.ini in your %userprofile% and makes copys of your bookmarks.html to c:\-=Mozzila Firefox backup=-\ with all subfolders of any profiles you have.
I know theres a program to backup your profile but not many people use or know for that program.

or an extension to firefox

bookmark backup

backups up other things in the firefox folder too