选择一个class属性的起始值="top"的所有元素 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <style>
    [class|=top] {
      background: yellow;
    }
  </style>
</head>

<body>
  <h1 class="top-header">Welcome</h1>
  <p class="top-text">Hello world!</p>
  <p class="content">Are you learning CSS?</p>

  <p><b>Note:</b> For [<i>attribute</i>|=<i>value</i>] to work in IE8 and earlier, a DOCTYPE must be declared.</p>

</body>
</html>
        