<div style="width: 200px; border: 10px solid #666; background-color: #fff;">
<div style="height: 100px; display: table-cell; vertical-align: middle;">
<h1 style="font-size: 12px;">Block element, with long enough content to wrap.</h1>
</div>
</div>

OR

http://css-tricks.com/centering-percentage-widthheight-elements/