CSS:
<style type="text/css">
.align_center_outer{
margin:0 auto;
}
.align_center_inner{
width:200px;
margin:0 auto;
}
.vertical_middle{
height:400px;
display:table-cell;
vertical-align: middle;
margin-top:expression((400-this.height)/2);
}
</style>
HTML:
<body>
<div class="align_center_outer" style="border:solid 1px red;width:800px;height:400px;">
<div class="align_center_inner" style="border:solid 1px green;">
<div class="vertical_middle">
<div class="">aaaa</div>
<div class="">aaaa</div>
<div class="">aaaa</div>
</div>
</div>
</div>
</body>