在线运行代码 - 菜鸟教程

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"> 
<title>菜鸟教程(cainiaoplay.com)</title>
<style>p:nth-child(3n+0)
{
	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>
<p>The fifth paragraph.</p>
<p>The sixth paragraph.</p>
<p>The seventh paragraph.</p>
<p>The eight paragraph.</p>
<p>The ninth paragraph.</p>

<p><b>注意:</b> Internet Explorer 8以及更早版本的浏览器不支持:nth-child()选择器.</p>

</body>
</html>
源代码

动行结果
