Sometimes the Firefox window size is miscalculated. Normally if you maximize the window, it is fit to the screen, but this only helps if you have a way to maximize the window. On Windows, you can press Alt+Spacebar and then x to do it even if you can't see the title bar buttons. Not sure what options you might have on Linux. Otherwise, you might need to delete a settings file that stores the default window position, '''xulstore.json'''. That is in your currently active profile folder. [[Profiles - Where Firefox stores your bookmarks, passwords and other user data]]