* {
	margin:0px;
	padding:0px;
}
.box {
	width:300px;
	height:40px;
	border:1px solid #666;
	margin:100px;
	position:relative;
	overflow:hidden;
}
.list_menu {
	width:1200px;
	list-style:none;
	overflow:hidden;
}
.list_menu li {
	float:left;
	width:150px;
	text-align:center;
	height:40px;
	line-height:40px;
}
.lef,.rig {
	position:absolute;
	width:30px;
	text-align:center;
	height:40px;
	line-height:40px;
	background:#aaa;
	color:#fff;
	cursor:pointer;
}
.lef {
	top:0px;
	left:0px;
}
.rig {
	top:0px;
	right:0px;
}