A closed thread on here looks to address a problem whereby the addon bar is open by default: http://support.mozilla.org/en-US/questions/780650 The solutions related to xmarks, among others, but this can also be caused by academic reference manager plugin Zotero. To remedy, type "about:config" without the quotes, in your address bar, paste this: extensions.zotero.statusBarIcon into the filter bar (selected by default) and change the integer to 0 i would have added this to the thread which, despite being old, is still a valuable resource. If mods can add this, that would be helpful. If not, hopefully this'll be found by people searching, and help them.