DIV垂直居中对齐

效果图：

CSS:

 #container{
        display:table-cell; 
        300px; 
        height:300px; 
        vertical-align:middle; 
        border:1px solid #ccc; 
        border-radius:20px;
        text-align:center; 
}
#cell{
        margin: 0 auto; 
        100px; 
        height:100px; 
        border:1px solid red; 
        border-radius:10px;
 }

HTML:

 <div id="container">
        <div id="cell"></div>
 </div>