加了shopClass_show 它立马跑左上角去了。。怎么的？

Question

/*navBox*/

.navBox{background-color:#0066CC; height:35px; color:#fff;}

.shopClass{ width:190px; }

.shopClass h3{text-align:center;line-height:35px;}

.shopClass i{width:11px; height:7px; overflow:hidden; background:url(../images/icon/down.jpg) left center no-repeat; display:inline-block; margin-left:11px;}

.nav,.shopClass{font-family:"微软雅黑";font-size:12px; }

.nav{line-height:35px;}

.nav li{float:left;}

.nav a{height:35px; display:inline-block; padding:0 35px; color:#FFF;text-decoration: none}

.nav .active{ background-color:#3399FF;}

/*商品弹出*/

.shopClass_show{background-color:#3399FF; position:absolute; left:0;top:35px; witdh:100%;}

.shopClass_item{padding:14px 10px; border-bottom:#3487f2 solid 1px; border-top:#5aa1fe solid 1px;}

.shopClass_item dt{height:22px; background:url(../images/icon/right.png) right center no-repeat;}

.shopClass_item .b{font:14px/1 "微软雅黑";}

.shopClass_item a{color:#fff; }

.shopClass_item .alink{ width:48px; height:20px; background:url(../images/icon/alink_bg.png) left center no-repeat; display:inline-block; text-align:center; line-height:20px; text-decoration:underline;}

<div class="navBox">

     <div class="comWidth">

   <div class="shopClass fl">

      <h3>全部商品分类<i></i></h3>

  <div class="shopClass_show">

     <dl class="shopClass_item">

     <dt><a href="#" class="b">手机</a> <a href="#" class="b">数码</a> <a href="#" class="alink">合约机</a>

 </dt>

 <dd><a href="#">荣耀3X</a> <a href="#">单反</a> <a href="#">合智能设备</a>

 </dd>

 </dl>

</div>

   </div>

   <ul class="nav fl">

      <li><a href="#" class="active">数码城</a></li>

  <li><a href="#">天黑黑</a></li>

  <li><a href="#">团购</a></li>

  <li><a href="#">发现</a></li>

  <li><a href="#">二手特卖</a></li>

  <li><a href="#">名品会</a></li>

</ul>

 </div>

  </div>