Hi Jan, that's strange. Do you mean the kind of full screen for videos (click a button, press Esc to cancel) or the browser full screen you enter/exit using the F11 function key? If you launch a new Firefox window using Ctrl+N, does it have its normal toolbars? Is the problem on an "attack" page that wants you to call a number or click a link, or just a normal page? In the past, users have reported attack pages that kept going to full screen every time you moved your mouse. To close an attack page, try pressing the close tab keyboard shortcut Ctrl+W. Also, I think the Windows key + D will minimize everything and show the desktop, which hopefully would allow you to manage Firefox windows using the Taskbar icon.