Dunno why but in firefox 3 after adding a tag to a bookmark, later on, I haven’t been able to delete it no matter what I tried… hopefully there IS a solution.
1) download firefox extension: SQLLite
2) run it.
3) at the top right of screen, choose places.sqllite, click go.
4) select Tables -> moz_bookmarks
5) click browse&search tab, and then click on search
6) under “6. title=” box enter “nameOfYourTag”
7) right click -> delete.
It’s funny mozzila dedevelopers didn’t integrate the option for this…
Thanks to people who found a way to fix tags.