Do you see that button if you open the Customize window? * Open the Customize window via "View > Toolbars > Customize" or via "Firefox > Options > Toolbar Layout" * If a missing item is in the toolbar palette then drag it back from the Customize window on the toolbar * If you do not see an item on a toolbar and in the toolbar palette then click the "Restore Default Set" button to restore the default toolbar set up. See also: * http://kb.mozillazine.org/Toolbar_customization * http://kb.mozillazine.org/Corrupt_localstore.rdf