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        <title>菜鸟教程(runoob.com)</title> 
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            <h2>排版</h2>
            <p>设置 pre 元素可滚动:</p>
            <pre class="pre-scrollable">
        内容可滚动
        Text in a pre element
        is displayed in a fixed-width
        font, and it preserves
        both      spaces and
        line breaks.
        Text in a pre element
        is displayed in a fixed-width
        font, and it preserves
        both      spaces and
        line breaks.
            </pre>
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