And yet, to this day, Firefox has both Ctrl-Q (close all Firefox windows without prompting) and its neighbor Ctrl-W (close current tab) and refuses to change that or provide remappable keyboard shortcuts. One of the biggest UI failures I'm aware of in 2014.
This in combination with "Restore all tabs on startup" not being the default is a disaster.
The first thing I do on a new Firefox installation is enable "Restore all tabs on startup".
Even without that flag enabled, you can restore all tabs when closing/reopening Firefox.
History > Restore Closed tabs.
Thanks, good to know.
This is in all apps in OS X, that's the standard keymapping.
And given that it's right next to a 'single terminal reset' key, it should be immediately obvious to anyone who's ever used a keyboard - mistakes can and do happen, even when you're fluent.