If you have the menu bar visible, normally, holding Alt + F brings up the file menu. Much to my dismay, when browsing any Youtube video page, Alt + F caused it to go fullscreen instead. Actually, if you look very carefully, it brings up the file menu bar, and then immediately maximizes the window also. It looks like Youtube has chosen the ALT-F combination for the full screen feature. IMO, the browser should not allow applications to hijack the built-in keyboard shortcuts, such as ALT-F. ALT + F should always bring up the File menu within Firefox, and should not trigger any function .
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