CSS 垂直居中五种实现方法

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步骤二：
现在我们开始用一些基本的 CSS 来给页面添加样式。把以下代码放入在我们的 html 页面顶部被引入的 style.css。

html, body {
 margin:0; padding:0;
 height:100%;
}
 
body {
 background:url('page_bg.jpg') 50% 50% no-repeat #FC3;
 font-family:Georgia, Times, serifs;
}
 
#floater {
 position:relative; float:left;
 height:50%; margin-bottom:-200px;
 width:1px;
}
 
#centered {
 position:relative; clear:left;
 height:400px; width:80%; max-width:800px; min-width:400px;
 margin:0 auto;
 background:#fff;
 border:4px solid #666;
}
 
#bottom {
 position:absolute;
 bottom:0; right:0;
}
 
#nav {
 position:absolute; left:0; top:0; bottom:0; right:70%;
 padding:20px; margin:10px;
}
 
#content {
 position:absolute; left:30%; right:0; top:0; bottom:0;
 overflow:auto; height:340px;
 padding:20px; margin:10px;
}

在我们能够把 content 垂直居中之前， body 和 html 应该被拉伸到 100％ 的高度。由于 height
在 padding 和 margin 之内，所以我们要把它们设成 0 以防止因为很小的 margin 出现滚动条。