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<html>3
<head>4
<meta charset="utf-8">5
<style>6
p:nth-child(2) {7
background: #ff0000;8
}9
</style>10
</head>11
<body>12
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<h1>This is a heading</h1>14
<p>The first paragraph.</p>15
<p>The second paragraph.</p>16
<p>The third paragraph.</p>17
<p>The fourth paragraph.</p>18
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<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>20
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</body>22
</html>