案例：CSS3 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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<head>
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<style type="text/css">
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p.normal {font-weight: normal}
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p.thick {font-weight: bold}
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p.thicker {font-weight: 900}
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</style>
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</head>
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​
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<body>
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<p class="normal">This is a paragraph</p>
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​
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<p class="thick">This is a paragraph</p>
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​
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<p class="thicker">This is a paragraph</p>
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</body>
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​
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</html>
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​