<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>啥也不是</title>
    <style>
      *{
   
          margin: 0;
          padding: 0;
      }
      li{
   
          list-style: none;
      }
      .top{
   
          height: 50px;
          background-color: gray;
      }
      .banner{
   
          width: 980px;
          height: 150px;
          background-color: gray;
          margin: 10px auto;
      }
      .box{
   
          width:980px;
          margin: 0 auto;
          height: 300px;
        }
        .box li{
   
            float: left;
            width: 237px;
            height: 300px;
            background-color: gray;
            margin-right: 10px;
        }
        .box .last{
   
            margin-right: 0px;
        }
        /* 只要是通栏的盒子(和浏览器一样宽)不需要指定宽度 */
        .footer{
   
            height: 200px;
            background-color: gray;
            margin-top: 10px;
        }
    </style>
</head>
<body>
    <div class="top"></div>
    <div class="banner"></div>
    <div class="box">
        <ul>
            <li></li>
            <li></li>
            <li></li>
            <li class="last"></li>
        </ul>
    </div>
    <div class="footer"></div>
</body>
</html>