​x
 
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
* {
  box-sizing: border-box;
}
​
.header {
  border: 1px solid red;
  padding: 15px;
}
​
.menu {
  width: 25%;
  float: left;
  padding: 15px;
  border: 1px solid red;
}
​
.main {
  width: 75%;
  float: left;
  padding: 15px;
  border: 1px solid red;
}
</style>
</head>
<body>
​
<div class="header">
  <h1>Shanghai</h1>
</div>
​
<div class="menu">
  <ul>
    <li>The Flight</li>
    <li>The City</li>
    <li>The Island</li>
    <li>The Food</li>
  </ul>
</div>
​
<div class="main">
  <h1>The City</h1>
  <p>Shanghai is one of the four direct-administered municipalities of the People's Republic of China. Welcome to Shanghai!
</p>
  <p>请调整浏览器窗口的大小，来查看内容如何响应调整大小。</p>
</div>
​
</body>
</html>
​