Tab is supposed to autocomplete a username you've started typing out, but this functionality doesn't work in firefox.

Doing it gives this error in console:

ReferenceError: event is not defined[Learn More] mafia_game.js:1:114544 <anonymous> https://epicmafia.com/javascripts/m/mafia_game.js:1:114544 n.event.dispatch https://epicmafia.com/javascripts/jquery/jquery2.js:1:39469 n.event.add/r.handle https://epicmafia.com/javascripts/jquery/jquery2.js:1:37585

This seems to be relevant to fixing it:

http://stackoverflow.com/questions/20522887/referenceerror-event-is-not-defined-error-in-firefox