#box img {
	width:200px;
	height:115px;
	border:2px solid #000;
	cursor:pointer;
}
li {
	padding:0;
	margin:0;
	float:left;
	list-style:none;
	margin-right:10px;
	position:relative;
}
li .btn {
	display:none;
	width:202px;
	height:40px;
	background-color:#000;
	position:absolute;
	top:0;
	left:0;
	opacity:0.6;
}
li .btn a {
	display:block;
	width:30px;
	height:20px;
	background-color:red;
}
li .btn a.previous {
	float:left;
}
li .btn a.next {
	float:right;
}