指定其父级的第一个p元素的背景色 - 在线编辑器

          <!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <style>
    p:first-of-type {
      background: #ff0000;
    }
  </style>
</head>
<body>

  <h1>This is a heading</h1>
  <p>The first paragraph.</p>
  <p>The second paragraph.</p>
  <p>The third paragraph.</p>
  <p>The fourth paragraph.</p>

</body>
</html>
        