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    <title>菜鸟教程(runoob.com)</title> 
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    <h2>按钮</h2>
    <p>.btn-sm 类制作小按钮:</p>            
    <button type="button" class="btn btn-default btn-sm">小的默认按钮</button>
    <button type="button" class="btn btn-info btn-sm">小的信息按钮</button>      
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