以下大图片和小图片将显示在不同设备上 - 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>
    /* For width smaller than 400px: */

    body {
      background-repeat: no-repeat;
      background-image: url('/wp-content/uploads/2015/06/img_smallflower.jpg');
    }
    /* For width 400px and larger: */

    @media only screen and (min-width: 400px) {
      body {
        background-image: url('/wp-content/uploads/2015/06/img_flowers.jpg');
      }
    }
  </style>
</head>
<body>

  <p style="margin-top:360px;">调整浏览器宽度，背景图片在小于 400 px 时将改变。</p>

</body>
</html>
        