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<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
<style>
p{height:30px;border:1px solid #000;}
body *:nth-child(1){margin-left:10px;}/* 无论何种类型都选择第一个 */
p:nth-child(1){color:#fff;}
p:first-child{padding:20px;}
p:nth-last-child(1){color:#fff;}
p:last-child{padding-left:20px;}
p:nth-child(odd){background:red;}
p:nth-child(even){background:blue;}
h2:nth-of-type(2){background: green;}
p:nth-last-of-type(3){color:#999;}
h3:first-of-type{color:pink;}
h2:last-of-type{color:#fff;}
p:empty{height:40px;border:10px solid green;}
p *:only-child{border:10px dashed pink;}
p *:only-of-type{border:10px dashed pink;}
</style>
</head>
<body>
<p>p1</p>
<h1>h1</h1>
<p>p2</p>
<h2>h2</h2>
<p>p3</p>
<h3>h3</h3>
<p>p4</p>
<h2>h222</h2>
<p>p5</p>
<p></p>
<p><span>123</span></p>
<p><span>123</span><a>456</a></p>
</body>
</html>
E:empty 表示E元素中没有子节点。注意：子节点包含文本节点
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原文地址：http://www.cnblogs.com/slp-qm/p/5236591.html
