User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36 Steps to reproduce: I define a css style like below: .btn:active { border: 1px solid #B2B2B2; } the :active pseudo class can be trigger when press space, it's ok in IE and chrome, only firefox can't trigger it, and it works OK for mousedown. Actual results: the :active pseudo class can be trigger when press space, it's ok in IE and chrome, only firefox can't trigger it, and it works OK for mousedown. Expected results: the :active pseudo class can be trigger when press space.