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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​
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<body bgcolor="yellow">
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<h2>This is a heading</h2>
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<p>This is a paragraph.</p>
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<p>The old bgcolor attribute only works on the body element.</p>
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<p>For future proof HTML, use styles instead:</p>
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</body>
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​
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</html>
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​