User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20171023180840 Steps to reproduce: It happened waay to many times for me: I intended to close one tab with ctrl+w, but my finger slipped and I've pressed ctrl+q instead. Actual results: The browser closes immediatly. Expected results: Two options: * nothing (we already have a shortcut for closing the window: alt+f4) * at least display a warning message so the closedown can be cancelled. It would be nice to at least have an option to disable the shortcut (I've tries some extensions that claim to do that, but they don't work)