Vertical centering with CSS
I wrote this post a while back. The content can still be relevant but the information I've linked to may not be available.
Aligning an element so that is is vertically centered should be something that is quite easy but CSS makes it more difficult than it should be! Not to worry, Douglas Heriot describes a variety of different methods for achieving vertical centering and explains the pros and cons of each method.
File for future reference.