Firefox menus that extend beyond the bottom of the firefox window do not go away when the program closes. they remain on the screen.
When a menu like file or bookmarks is open and the bottom of the menu extends below the bottom of the firefox window, after the menu is closed by making a selection on it or by clicking on another menu, the portion of the menu that extended below the firefox window persists on the desk top. It will stay there even if the firefox window is moved or closed. I'd paste in a screen shot but this report tool doesn't seem to take images.
When a menu like file or bookmarks is open and the bottom of the menu extends below the bottom of the firefox window, after the menu is closed by making a selection on it or by clicking on another menu, the portion of the menu that extended below the firefox window persists on the desk top. It will stay there even if the firefox window is moved or closed. I'd paste in a screen shot but this report tool doesn't seem to take images.