.atras {
	position:absolute;
	left:5px;
	z-index:1;
	padding-top:5px;
	padding-left:5px;
	padding-right:10px;
	padding-bottom:20px;
	border:1px;
	border-style:solid;
	background-color:#3399ff;
	}
	
.medio {
	position:absolute;
	left:10px;
	z-index:2;
	padding-top:5px;
	padding-left:5px;
	padding-right:10px;
	padding-bottom:20px;
	margin-top:20px;
	margin-left:20px;
	border:1px;
	border-style:solid;
	background-color:#99CCFF;
	}
	
.delante {
	position:absolute;
	left:15px;
	z-index:3;
	padding-top:5px;
	padding-left:5px;
	padding-right:10px;
	padding-bottom:20px;
	margin-top:40px;
	margin-left:40px;
	border:1px;
	border-style:solid;
	background-color:#ffffff;
	}