I didn't know that I needed this add-on until I found it. IMHO, it is the best Firefox extension that I have ever seen. Very highly recommended, obviously.

Incidentally, though the add-on works fine "as is", the dev is amazing in how quickly he responds to questions and suggestions. Just e-mail him at daniel.rb.lobo+sss@gmail.com, as AMO reviews are not the right place to ask for help.