求大神帮忙看下id="guang"的样式怎么显示不出来？

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>产品介绍</title>
<style type="text/css">
a{
   text-decoration:none;}
body{
   background:#f0f0f0;
   margin:0;
   padding:0;
   }
#top{
   width:100%;
   background:url(images/%E7%81%AB%E7%8B%90%E6%88%AA%E5%9B%BE_2016-04-15T06-19-35_02.png)
   }
#top .top_top{
   width:980px;
   height:30px;
   /*border:1px solid red;*/
   margin:0 auto;
   }
#top .top_top .top_left{
   font-size:14px;
   font-family:"微软雅黑";
   line-height:25px;
   float:left;
   }
#top .top_top .top_right{
   float:right;
   }
#top .top_top .top_right span img{
   margin-top:4px;}
#top .top_top .top_right a{
   margin-left:2px;
   color:#000;
   font-size:14px;
   font-family:"微软雅黑";
   line-height:30px;
   }
#top .top_top .top_right a:hover{
   color:#F00;}




#guang{
   width:980px;
   height:200px;
   border:1px solid red;}
</style>
</head>

<body>
<div id="top">
   <div class="top_top">
       <div class="top_left">欢迎光临电商平台服务中心！</div>
        <div class="top_right"><span><img src="images/火狐截图_2016-04-15T06-19-35_05.png" alt=""/><a href="#">设为首页</a></span>
                               <span><img src="images/火狐截图_2016-04-15T06-19-35_07.png" alt=""/><a href="#">加入收藏</a></span>
                                <span><a href="#">服务商登陆</a></span>
                               </div>
     </div>
</div>


<div id="guang"><img src="images/火狐截图_2016-04-15T06-19-35_03.png"/>
</div>

</body>
</html>
加下划线的部分，id=“guang”，为什么显示不出来样式，求大神帮忙看看