让整个table居于页面正中间（上下，左右都居中）

<table width= "300 " height= "200 "

style= "position:absolute;z-index:1;left:expression((document.body.clientWidth-this.offsetWidth)/2);top:expression((document.body.clientHeight-this.offsetHeight)/2) ">

<tr>

< td>   </td>

</tr>

</table>