On the Add A New Certificate page, for "unauthorized websites", if you click on the "View certificate" button the window automatically resizes for a bigger size, eventually it turns out to get out of screen reach and you can't see the whole window anymore. The problem is that the (Shift+F4) Size option is greyed out, and you can't resize the window with your mouse too. Also, starting Mozilla with a bigger administration level puts everything back to default, the window does too, but when I resynchronize my configurations, it gets back to its immense size. There's a topic on a different website that talks about this, yet it has never been correctly answered. Here's the link: https://superuser.com/questions/1253507/windows-firefox-security-exception-window-resizing-itself