To sum it up, there are few approaches to align content vertically in container. These are main approaches (if you now some completely different way to do it, it would be ve
If you know the height of what you are centering you can use absolutely position the box 50% from the top and then use a negative margin half the height of the box to center it. It's annoyingly complex getting it to work it ie7 but it does work.
http://css-tricks.com/snippets/css/exactly-center-an-imagediv-horizontally-and-vertically/
Example:
.center {
width: 300px;
height: 300px;
position: absolute;
left: 50%;
top: 50%;
margin-left: -150px;
margin-top: -150px;
}