div {
	position: relative;
	
	/* box model */
	margin-right: auto;
	margin-bottom: 320px;
	margin-left: auto;
	width: 640px;
	height: 640px;
	border: 0;
	padding: 0;

	background: url(img/birds.gif) no-repeat center;
}

div img {
	position: absolute;
	top: 100px;
	left: 250px; 
}