#background{
	height:480;
	width:640;
	position:absolute;
	left:50%;
	margin-left:-320px;
	top:50%;
	margin-top:-240px;
}
#portfolio a img{
	height:75px;
	width:268px;
	border:none;
	position:absolute;
	left:50%;
	margin-left:-133px;
	top:50%;
	margin-top:21px;
}