当浏览器的宽度在 520 到 699px, 邮箱链接前添加邮件图标 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <style>
    ul {
      list-style-type: none;
    }

    ul li a {
      color: green;
      text-decoration: none;
      padding: 3px;
      display: block;
    }

    @media screen and (max-width: 699px) and (min-width: 520px) {
      ul li a {
        padding-left: 30px;
        background: url(email-icon.png) left center no-repeat;
      }
    }
  </style>
</head>
<body>

  <h1>重置浏览器窗口，查看效果!</h1>

  <ul>
    <li><a data-email="johndoe@example.com" href="mailto:johndoe@example.com">John Doe</a></li>
    <li><a data-email="marymoe@example.com" href="mailto:marymoe@example.com">Mary Moe</a></li>
    <li><a data-email="amandapanda@example.com" href="mailto:amandapanda@example.com">Amanda Panda</a></li>
  </ul>

</body>
</html>
        