To hide/customize your toolbars in firefox navigate to View>Toolbars>Customize
This allows you to pull anything off the screen you see into the toolbars popup window to remove the toolbar/icon from view.
Alternatively you can move toolbars or add buttons ect.
Also if you want to ever run firefox without addons or toolbars ect hold down Shift when opening firefox, this will enable safemode disabling everything known to firefox.
Also the addon's manager can be used to permanently remove addons, extentions, plugins and appearance tabs to find the annoying toolbar.
Also in the view/toolbars tab you can hide/show the menu bar, this allows for freeing up some viewing area or allow you to stop using the top left firefox button or pushing Alt to show the menu.