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這是我的代碼:不生效?
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
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<p>Donec id elit non mi porta gravida at eget metus. Fusce dapibus,</p>
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<div style={{border: 'solid black 0.5px'}} class="col-md-3 offset-md-4">
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<p>Donec id elit non mi porta gravida at eget metus. Fusce dapibus, </p>
<p><a className="btn btn-secondary" href="#" role="button">View details »</a></p>
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<div style={{border: 'solid black 0.5px'}} class="col-md-3 offset-md-1">
<h2>Heading 2</h2>
<p>Donec id elit non mi porta gravida at eget metus. Fusce dapibus, </p>
<p><a className="btn btn-secondary" href="#" role="button">View details »</a></p>
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我用的標題2,一個在中心偏移,但它不會跳過一些空間,不像在文檔?我想要做的是在它們上添加一些邊距,但是當我嘗試時,它會將底部的最後一個壓入底部,或者如果我不使用4,它不佔用所有空間。我如何在這裏添加保證金?