difference between Firefox and Chrome padding

If your .button is a button this might be a mozilla inner focus thing... try this?

.button::-moz-focus-inner { border: 0; padding: 0; margin:0; }

The focus-inner fix works but I also add negative top and bottom margins to get it to the right height. e.g.:

*::-moz-focus-inner {
padding: 0;
border: 0;
margin-top:-1px;
margin-bottom:-1px;
}

I used to love Firefox, but it has become a bloated mess and fell off my Christmas list years ago.

Firefox and Chrome render padding exactly the same way. Your problem is elsewhere.

Are you using a reset CSS? If not, the default line-height declaration might be interfering with the rendering of your button.

For one, your height is way smaller than your font-size. Since you don't have overflow specified, your height will always be extended to at least font-size (or whatever your line-height specifies).

If your .button class is actually a <button> element, also apply superUntitled fix.