#zum {
width: 220px;
background: url(../images/retiro/m.jpg) 0 0 no-repeat;
margin: 0;
padding: 0;
}
#thumb a {
	height: 90px; 
	display: block;
	}
#thumb a:hover { 
	width: 700px; 
	height: 391px; 
	background: transparent url(../images/retiro/mapasitio.jpg) no-repeat;
	}