请老师帮忙检查下代码并解答下疑惑

来源：5-2 编程练习

人生的起源

2019-07-27 00:22:09

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title></title>
    <style>
     /* 在此处补充代码*/
     * { margin: 0; padding: 0; }
     ul, li { list-style: none; }
     header {
        background: #000;
        display: flex;
        justify-content: space-around;
        align-items: center;
     }
     .nav {
        color: #fff;
        flex-basis: 636px;
        display: flex;
        justify-content: space-between;
     }
     .nav li {
        font-size: 30px;
     }
     .login {
        flex-basis: 154px;
        display: flex;
        justify-content: space-between;
     }
     .login input {
        border: 0;
        background: #ffa500;
        color: #fff;
        font-size: 24px;
        border-radius: 4px;
        padding: 5px;
        cursor: pointer;
     }
     section {
        height: 460px;
        display: flex;
        flex-wrap: wrap;
        justify-content: space-around;
        align-content: space-around;
     }
     .section {
        background: #add8e6;
        border-radius: 10px;
        font-size: 24px;
        height: 200px;
        flex-basis: 864px;
        display: flex;
        justify-content: space-around;
     }
     .section .box {
        flex-basis: 492px;
        display: flex;
        flex-direction: column;
        justify-content: space-around;
     }
     .section .shopping {
        display: flex;
        align-items: center;
     }
     .section .btn {
        font-size: 24px;
        background: #ffa500;
        color: #fff;
        border-radius: 10px;
        padding: 15px;
        cursor: pointer;
     }
    </style>
</head>
<body>
<!-- 头部 -->
   <header>
     <div class="logo">
       <img src="http://climg.mukewang.com/59197ab000014f1503000100.jpg" alt="">
     </div>
       <ul class="nav">
         <li>课程</li>
         <li>路径</li>
         <li>猿问</li>
         <li>手记</li>
       </ul>     
     <div class="login">
       <input type="button" value="登录">
       <input type="button" value="注册">
     </div>
   </header>
<!-- 主体内容 -->
   <section>
    <div class="section">
      <div class="box">
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      </div>
      <div class="shopping">
        <div class="btn">加入购物车</div>
      </div>
    </div>
    <div class="section">
      <div class="box">
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      </div>
      <div class="shopping">
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      </div>
    </div>
    <div class="section">
      <div class="box">
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      </div>
      <div class="shopping">
        <div class="btn">加入购物车</div>
      </div>
    </div>
    <div class="section">
      <div class="box">
        <p>《从H5网页开发到移动端响应式开发》</p>
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      </div>
      <div class="shopping">
        <div class="btn">加入购物车</div>
      </div>
    </div>
    </section>  
</body>
</html>

请老师帮忙看下代码还有什么需要改进的，并帮忙解答个问题