#box
{
	width: 150px;
	height: 150px;
	background: #FFF;
	border: red dotted 5px;
	text-align: center;
	position: absolute;
	margin-left: -75px;
	margin-top: -75px;
	left: 50%;
	top: 50%;
	z-index: 20;
	display: none;
}

#screen
{
	position: absolute;
	left: 0;
	top: 0;
	background: #000;
}