这里是要实现导航的左侧并选中的，此功能需引用jquery

左侧导航：

<div class="box">
<ul class="menu">
<li class="level1">
<a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >衬衫</a>
<ul class="level2">
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >短袖衬衫</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >长袖衬衫</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >短袖T恤</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >长袖T恤</a></li>
</ul>
</li>
<li class="level1">
<a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >卫衣</a>
<ul class="level2">
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >开襟卫衣</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >套头卫衣</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >运动卫衣</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >童装卫衣</a></li>
</ul>
</li>
<li class="level1">
<a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >裤子</a>
<ul class="level2">
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >短裤</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >休闲裤</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >牛仔裤</a></li>
<li><a href="#none" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >免烫卡其裤</a></li>
</ul>
</li>
</ul>
</div>
js代码：
<script type="text/javascript">
//等待dom元素加载完毕.
$(document).ready(function(){
$(".level1 > a").click(function(){
$(this).addClass("current") //给当前元素添加"current"样式
.next().show() //下一个元素显示
.parent().siblings().children("a").removeClass("current") //父元素的兄弟元素的子元素<a>移除"current"样式
.next().hide(); //它们的下一个元素隐藏
return false;
}); 
});
</script>

/* reset */
body{margin:0;padding:0 0 12px 0;font-size:12px;line-height:22px;font-family:"\5b8b\4f53","Arial Narrow";background:#fff;}
form,ul,li,p,h1,h2,h3,h4,h5,h6{margin:0;padding:0;}
input,select{font-size:12px;line-height:16px;}
img{border:0;}
ul,li{list-style-type:none;}
a {color:#00007F;text-decoration:none;}
a:hover {color:#bd0a01;text-decoration:underline;}

.box {
width: 150px;
margin: 0 auto;
}
.menu{
overflow:hidden;
border-color: #C4D5DF;
border-style: solid;
border-width: 0 1px 1px;
}
/* lv1 */
.menu li.level1 a{
display: block;
height: 28px;
line-height: 28px;
background:#EBF3F8;
font-weight:700;
color: #5893B7;
text-indent: 14px;
border-top: 1px solid #C4D5DF;
}
.menu li.level1 a:hover{text-decoration:none;}
.menu li.level1 a.current{background:#B1D7EF;}
/* lv2 */
.menu li ul{overflow:hidden;}
.menu li ul.level2{display:none;}
.menu li ul.level2 li a{
display: block;
height: 28px;
line-height: 28px;
background:#ffffff;
font-weight:400;
color: #42556B;
text-indent: 18px;
border-top: 0px solid #ffffff;
overflow: hidden;
}
.menu li ul.level2 li a:hover{
color:#f60;
}

<script type="text/javascript"> 
$(document).ready(function(){ 
$(".level2 a").each(function(){ 
$this = $(this); 
if($this[0].href==String(window.location)){ 
$this.addClass("hover"); 
} 
}); 
}); 
</script>