I've never had my bookmarks, download history, or cookies disappear, but it's somewhat common to see my browsing history go up in smoke after closing and restarting Firefox.
Name:
Anonymous2007-02-21 4:32 ID:w4nUx9HI
i use del.icio.us bookmarks in firefox. i won't loose them
Name:
Anonymous2007-02-21 5:36 ID:i5FiHPiN
>>1
Perhaps you reseted your computer somehow (poweroff, whatever) without letting Firefox write its files properly and the Windows system cache write the data to disk. I recall there's a bookmark file backup, look for the mozilla directory somewhere in \Documents and settings\your_user, enter a random named directory (something like w3mv013x.slt, with different characters), and look for the bookmarks file. There should be a backup nearby.