案例:html案例     状态:可编辑再运行    进入竖版
 运行结果 
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<html>
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<body style="background-color:yellow">
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<h2 style="background-color:red">This is a heading</h2>
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<p style="background-color:green">This is a paragraph.</p>
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</body>
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</html>
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