<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Strict//EN” 
“http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd”>
<html xmlns=”http://www.w3.org/1999/xhtml” xml:lang=”en” 
lang=”en”> <head> <title>Centering site through 
html</title>

<style type=”text/css”>

body,html{
height:100%;
margin:0px;
padding:0px;
overflow:hidden;
}
.site{
height:100%;
background:#333;
}
.siteTd{
height:100%;
vertical-align:middle;
text-align:center;

}
.page{
margin:0 auto;
}
.pageTd{
height:400px;
}
</style>
</head>
<body>

<table width=”100%” border=”0″ cellspacing=”0″ cellpadding=”0″  class=”site”>
<tr>
<td   class=”siteTd”>
<table width=”1024″ border=”0″ cellspacing=”0″ cellpadding=”0″ bgcolor=”#999999″ class=”page”>
<tr>
<td  class=”pageTd”>&nbsp;</td>

</tr>
</table></td>
</tr>
</table>

</body>
</html>

Note : More important height 100% on html and body then height 100% on td of table