#main {
	width:100%;
	position: absolute;
}
#box {
	margin:200px auto;
	position: relative;
	width: 200px;
	height: 200px;
    overflow: hidden;
    background: #333;
}
#overlay {
	position: absolute;
	top: 200px;
	width: 200px;
	height: 200px;
}