代码编辑器：
x
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2
<meta charset="utf-8">3
<link href="/static/next/css/tryit.css?v=2017082407" rel="stylesheet"/> 4
<style> 5
p:last-of-type6
{7
background:#ff0000;8
}9
</style>10
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<h1>This is a heading</h1>12
<p>The first paragraph.</p>13
<p>The second paragraph.</p>14
<p>The third paragraph.</p>15
<p>The fourth paragraph.</p>16
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<footer>简单教程，简单编程<br/>Copyright © 简单教程 www.twle.cn</footer>18