.preload { width: 0px; height: 0px; border: 0px; padding: 0px; } 

span.rosso   {font-family: Helvetica; font-size: 12px; font-weight: bold; color: #FF0000; text-decoration: none;}

a.rollover {
 display: block;
 width: 100px;
 height: 30px;
 background-image: url(default.png);
}
a:hover {
 background-image: url(rollover.png);
}
a span {
 display: none;
}