From the Mozilla Developer Network:
Do not use this property on Web sites: not only is it non-standard, but its behavior change from one browser to another. Even the keyword none has not the same behavior on each form element on different browsers, and some doesn't support it at all.
Jeff, I'll provide a patch to remove this if it's something you will consider. I've experienced some wonkiness using a.button from what I think is due to the appearance property.