Here is a great explanation why vertical-align will most probably not do what an innocent mind might suspect:
Understanding vertical-align, or "How (Not) To Vertically Center Content"[
^]
The site also sports some samples of how to achieve the same e.g.:
<style type="text/css">
#myoutercontainer { position:relative }
#myinnercontainer { position:absolute; top:50%; height:10em; margin-top:-5em }
</style>
...
<div id="myoutercontainer">
<div id="myinnercontainer">
<p>Hey look! I'm vertically centered!</p>
<p>How sweet is this?!</p>
</div>
</div>
Regards,
— Manfred