在每列中指定 class， class="col-" 用于定义每列有几个 span - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta charset="utf-8">
  <style>
    * {
      box-sizing: border-box;
    }

    .header {
      border: 1px solid red;
      padding: 15px;
    }

    .row:after {
      content: "";
      clear: both;
      display: block;
    }

    [class*="col-"] {
      float: left;
      padding: 15px;
      border: 1px solid red;
    }

    .col-1 {
      width: 8.33%;
    }

    .col-2 {
      width: 16.66%;
    }

    .col-3 {
      width: 25%;
    }

    .col-4 {
      width: 33.33%;
    }

    .col-5 {
      width: 41.66%;
    }

    .col-6 {
      width: 50%;
    }

    .col-7 {
      width: 58.33%;
    }

    .col-8 {
      width: 66.66%;
    }

    .col-9 {
      width: 75%;
    }

    .col-10 {
      width: 83.33%;
    }

    .col-11 {
      width: 91.66%;
    }

    .col-12 {
      width: 100%;
    }
  </style>
</head>
<body>

  <div class="header">
    <h1>Chania</h1>
  </div>

  <div class="row">

    <div class="col-3">
      <ul>
        <li>The Flight</li>
        <li>The City</li>
        <li>The Island</li>
        <li>The Food</li>
      </ul>
    </div>

    <div class="col-9">
      <h1>The City</h1>
      <p>Chania is the capital of the Chania region on the island of Crete. The city can be divided in two parts, the old town and the modern city.</p>
      <p>Resize the browser window to see how the content respond to the resizing.</p>
    </div>

  </div>
</body>
</html>
        