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<style type="text/css">
body{margin:0;padding:0}
div{margin:-200px auto auto -275px;position:absolute;top:50%;left:50%;width:550px;height:400px;background:#ff6600;text-align:center;line-height:400px}
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<div>盒模型 div 布局的垂直居中（W3C 推薦方法）</div>
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