样式：
.content{position: absolute;top:60px;}
.title {text-align: center;font-size:16px;}
.title span{line-height:25px;}
.dir{font-size:14px;padding-left:15px;}
.nav ul{font-size: 14px;font-weight: bold;margin:0px;list-style:none;}
.nav ul li{padding-left:10px;line-height: 24px;}
.nav ul li a{display: inline-block;width:300px;}
.content{position: absolute;top:60px;
