CSS未知高度垂直居中 - 走看看

<!doctype html>
<html lang="en">  
  <head>  
    <meta charset="utf-8" />  
    <meta content="IE=8" http-equiv="X-UA-Compatible"/>  
    <title> CSS垂直居中</title>  
    <style type="text/css">  
      .container{  
        500px;/*装饰*/
        height:500px;  
        background:#B9D6FF;  
        border: 1px solid #CCC;  
      }  
       
    </style>  
  </head>  
  <body>  
    <h1>垂直居中（table）</h1>  
    <div class='container'>
        <table width="100%" height="100%">
            <tr>
               <td align="center" valign="middle">
                  <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/205314/r_iebug.jpg" />
               </td>
           </tr>
       </table> 
   </div>
     
  </body>  
</html>

好了，我们看其CSS实现。凡是table能做到的，CSS都能做的，但各浏览器在CSS的差异比较大，因此要兼容它们难度很大。这涉及许多细节，各种流啊，display的表现效果与CSS hack，IE早些年搞了大堆的私有属性，这也有待我们深一步挖掘。我们先看最简单的实现，背景图片法

背景图片法

<!doctype html>
<html>
<head>
<title> CSS垂直居中</title>
<style type="text/css">
.container {
  500px;
  height:500px;
  line-height:500px;
  background:#B9D6FF url(http://images.cnblogs.com/cnblogs_com/rubylouvre/205314/r_iebug.jpg)  no-repeat center center;
  border:1px solid #f00;
  text-align: center;
}
 
</style>
 
</head>
<body>
<h1>垂直居中</h1>
<div class="container">
    
</div>
</body>
</html>

CSS表达式法

<html lang="en">  
  <head>  
    <meta charset="utf-8" />  
    <meta content="IE=8" http-equiv="X-UA-Compatible"/>  
    <title>司徒正美 CSS垂直居中</title>  
    <style type="text/css">  
      .container{  
        /*IE8与标准游览器垂直对齐*/
        display: table-cell;
        vertical-align:middle; 
        500px;/*装饰*/
        height:500px;  
        background:#B9D6FF;  
        border: 1px solid #CCC;  
      }  
      .container img{  
        display:block;/*让其具备盒子模型*/
        margin:0 auto;  
        text-align:center;
        margin-top:expression((500 - this.height )/2);/*让IE567垂直对齐 */
      }  
    </style>  
  </head>  
  <body>  
    <h1>垂直居中（CSS表达式）</h1>  
    <div class="container">  
      <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/205314/r_iebug.jpg" />  
    </div>  
  </body>  
</html>

绝对定位法

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta content="IE=8" http-equiv="X-UA-Compatible"/>
    <title>司徒正美 CSS垂直居中</title>
    <style type="text/css">
      div {
       /*IE8与标准游览器垂直对齐*/
        display:table-cell;
        vertical-align:middle;
        overflow:hidden;
        position:relative;
        text-align:center;
        500px;/*装饰*/
        height:500px;
        border:1px solid #ccc;
        background:#B9D6FF;
      }
      div p {
        +position:absolute;
        top:50%
      }
      img {
        +position:relative;
        top:-50%;
        left:-50%;
      }
  
    </style>
  </head>
  <body>
    <h1>垂直居中(绝对定位)</h1>
    <div class="container">
      <p>
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/205314/r_iebug.jpg" />
      </p>
    </div>
  </body>
</html>

display:inline-block法

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta content="IE=8" http-equiv="X-UA-Compatible"/>
    <title>司徒正美 CSS垂直居中</title>
    <style type="text/css">
      div {
        display:table-cell;
        vertical-align:middle;
        text-align:center;
        500px;
        height:500px;
        background:#B9D6FF;
        border: 1px solid #CCC;
      }
 
    </style>
    <!--[if IE]>
<style type="text/css">
i {
    display:inline-block;
    height:100%;
    vertical-align:middle
    }
img {
    vertical-align:middle
    }
</style>
<![endif]-->
    
  </head>
  <body>
    <h1>垂直居中(inline-block法)</h1>
    <div class="container">
      <i></i>
      <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/205314/r_iebug.jpg" />
    </div>
  </body>
</html>

writing-mode法

<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta content="IE=8" http-equiv="X-UA-Compatible"/>
    <title> CSS垂直居中</title>
    <style type="text/css">
      div{
        500px;
        height:500px;
        line-height:500px;
        text-align:center;
        background:#B9D6FF;
        border:1px solid #f00;
      }
      div span{
        height:100%9;
        writing-mode:tb-rl9;
      }
      div img{
        vertical-align:middle
      }
    </style>
  </head>
  <body>
    <h1>垂直居中(writing-mode法)</h1>
    <div class="container">
      <span>
        <img src="http://images.cnblogs.com/cnblogs_com/rubylouvre/205314/r_iebug.jpg" />
      </span>
    </div>
  </body>
</html>