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>