Firefox is becoming one of the best web browsers, but improvements can be made.
A lot of the time tab's are clicked rappidly and then when browsing through them later on, the user forget's why the tab was opened in the first place. It would be usefull to add a editable text box to the top of the tab to label it with a description of what the page is, or a word that will remind the user what the tab is for. It may even be possible to pool all the titles people name there tab's and submitt it to a data base where web site's can have a collabortive description based on the titles people have given there tab's.
Two layers of tabs
When browsing the web lot's of tab's can be open, and squshed together. Having firefox open another layer of tab's to browse through will help web users.