Ever since I updated from Firefox 3.6 to 4.0 (and now 5.0) I had an additional item called “Bookmarks” in my Bookmarks toolbar. For me, it was (and is) unnecessary because I have all my bookmarks on my toolbar (and none of them in the actual Bookmarks menu). So, I was looking for a way to get rid of this button. I did some searching on the Internet but found nothing. So, I just tried to ignore this button.

Today, however, I stumbled over a way to remove this button. Just right-click on an empty space on the toolbar containing the address bar (not on the bookmarks toolbar). A menu will pop up and there you choose Customize.

This will allow you to add and/or remove toolbar buttons to Firefox’ main toolbar. Strangely, a new “Bookmarks” button will appear – usually on the right side.
This is the “Bookmarks” button that is displayed in your Bookmarks toolbar. Remove it (drag it away from the toolbar), close the “Customize” dialog, and the “Bookmarks” button will be gone.
Note: There are actually two bookmark buttons available in Firefox. One with a pulldown arrow to its right and one without. Only the one with the pulldown arrow will be moved to the bookmarks toolbar.
Thanks for the information as the content posted by you helped me removing the “Bookmarks” button from the toolbar.