I followed the instructions below and it doesn't work. I can delete individual sites in a folder but I can't delete it folder. It sits there empty. This is laborious in incomplete. What can be done to fix this? I use Firefox 16.0.2
Right-click the folder name and choose Delete. You can do this in either pane (left or right).
You might want to make a backup first. You can use the Backup... option or the Export to HTML option. (The Backup... option is more complete because it stores tags and some other additional information, but it is trickier to restore from the backup format without losing new bookmarks you may have added.)