Bookmark Backup is an extremely basic extension that creates a backup of the bookmarks file each time Firefox is closed. The backups can be found in the Firefox profile directory. They will be named bookmarks.html.{day} e.g. bookmarks.html.sun, bookmarks.html.mon, bookmarks.html.tue, etc.
If Firefox’s bookmarks become corrupted or lost simply find the backup for the previous day and rename it to bookmarks.html. (if necessary delete the corrupted version first).
