注意两组类样式是相同的，但名称不同 (col- 和 col-m-) - 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;
    }

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

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

    html {
      font-family: "Lucida Sans", sans-serif;
    }

    .header {
      background-color: #9933cc;
      color: #ffffff;
      padding: 15px;
    }

    .menu ul {
      list-style-type: none;
      margin: 0;
      padding: 0;
    }

    .menu li {
      padding: 8px;
      margin-bottom: 7px;
      background-color: #33b5e5;
      color: #ffffff;
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.12), 0 1px 2px rgba(0, 0, 0, 0.24);
    }

    .menu li:hover {
      background-color: #0099cc;
    }

    .aside {
      background-color: #33b5e5;
      padding: 15px;
      color: #ffffff;
      text-align: center;
      font-size: 14px;
      box-shadow: 0 1px 3px rgba(0, 0, 0, 0.12), 0 1px 2px rgba(0, 0, 0, 0.24);
    }

    .footer {
      background-color: #0099cc;
      color: #ffffff;
      text-align: center;
      font-size: 12px;
      padding: 15px;
    }
    /* For mobile phones: */

    [class*="col-"] {
      width: 100%;
    }

    @media only screen and (min-width: 600px) {
      /* For tablets: */
      .col-m-12 {
        width: 8.33%;
      }
      .col-m-2 {
        width: 16.66%;
      }
      .col-m-3 {
        width: 25%;
      }
      .col-m-4 {
        width: 33.33%;
      }
      .col-m-5 {
        width: 41.66%;
      }
      .col-m-6 {
        width: 50%;
      }
      .col-m-7 {
        width: 58.33%;
      }
      .col-m-8 {
        width: 66.66%;
      }
      .col-m-9 {
        width: 75%;
      }
      .col-m-10 {
        width: 83.33%;
      }
      .col-m-11 {
        width: 91.66%;
      }
      .col-m-12 {
        width: 100%;
      }
    }

    @media only screen and (min-width: 768px) {
      /* For desktop: */
      .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 col-m-3 menu">
      <ul>
        <li>The Flight</li>
        <li>The City</li>
        <li>The Island</li>
        <li>The Food</li>
      </ul>
    </div>

    <div class="col-6 col-m-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>
    </div>

    <div class="col-3 col-m-12">
      <div class="aside">
        <h2>What?</h2>
        <p>Chania is a city on the island of Crete.</p>
        <h2>Where?</h2>
        <p>Crete is a Greek island in the Mediterranean Sea.</p>
        <h2>How?</h2>
        <p>You can reach Chania airport from all over Europe.</p>
      </div>
    </div>

  </div>

  <div class="footer">
    <p>Resize the browser window to see how the content respond to the resizing.</p>
  </div>

</body>
</html>
        