I'm trying to do a sliding door button that can be used in general purpose everything works fine except the Firefox. the span element in button always lower 2px in FF.
here is example
Try this:
button::-moz-focus-inner {
border: 0;
padding: 0;
}
(Mind that the colon (:) is doubled, yes.)
The extra padding in this case is caused by an obscure Firefox bug.
(Having encountered this bug myself I've found the solution at this blog, via a Google search.)