.tooltip{
width: 200px; color:#000;
font:lighter 11px/1.3 Arial,sans-serif;
text-decoration:none;text-align:center;}

.tooltip span.top {
padding: 30px 8px 0px;
background-image: url(../img/struttura/bt.gif);
background-repeat: no-repeat;
background-position: top;
}

.tooltip b.bottom 
{
padding:3px 8px 15px;
color: #548912;
background-image: url(../img/struttura/bt.gif);
background-repeat: no-repeat;
background-position: bottom;
}