* {
	margin:0;
	padding:0;
	-webkit-box-sizing:border-box;
	-moz-box-sizing:border-box;
	box-sizing:border-box;
}
ul,ol,li {
	list-style:none;
}
.nav {
	width:400px;
	height:40px;
	background-color:papayawhip;
}
.nav_li {
	float:left;
	width:25%;
	height:100%;
	border:1px solid brown;
	margin-left:-1px;
	text-align:center;
	line-height:40px;
}
.con {
	height:400px;
	overflow:hidden;
	width:400px;
}
.con_li {
	width:400px;
	height:400px;
	display:none;
}