案例:html/html5 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>
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<h1 align="center">This is heading 1</h1>
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<h2 align="left">This is heading 2</h2>
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<h3 align="right">This is heading 3</h3>
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<h4 align="justify">This is heading 4</h4>
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</body>
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</html>
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