.costados {
	background-image: url(images/intro_costados.jpg);
	background-repeat: repeat-x;
	background-position: center top;
}
.der {
	background-image: url(images/intro_der.jpg);
	background-repeat: no-repeat;
	background-position: left center;
}
.izq {
	background-image: url(images/intro_izq.jpg);
	background-repeat: no-repeat;
	background-position: right top;
}

.center {
	background-image: url(images/intro_detras.jpg);
	height: 490px;
	width: 940px;
	background-position: center center;
	text-align: center;
	vertical-align: middle;
	margin:0 auto 0 auto;
}