I needed to do this ( source ):
input[type="submit"]::-moz-focus-inner,
input[type="button"]::-moz-focus-inner,
button::-moz-focus-inner { border : 0px; }
input[type="submit"]:focus,
input[type="button"]:focus { outline : none; }
I already had "outline: 0" set on everything with reset, but in order to get rid of the dashed line on the CSS-style button, I needed -moz-focus-inner.