I always just CSS style my submit buttons....
example:
input.submit {
margin: 0px;
padding: 0px;
background-color: transparent;
background-image: url(../images/common/button_submit.gif);
background-repeat: no-repeat;
height: 27px;
width: 51px;
border: 0px solid;
}
and the html:
<input type="submit" class="submit" value=" ">
works in FF 1.5, IE, Netscape, etc etc...