If you are looking at the new browsers(IE10+),
then you can make use of transform property to align a div at the center.
this is any div
And css for this should be:
.center-block {
top:50%;
left: 50%;
transform: translate3d(-50%,-50%, 0);
position: absolute;
}
The catch here is that you don't even have to specify the height and width of the div as it takes care by itself.
Also, if you want to position a div at the center of another div, then you can just specify the position of outer div as relative and then this CSS starts working for your div.
How it works:
When you specify left and top at 50%, the div goes at the the bottom right quarter of the page with its top-left end pinned at the center of the page.
This is because, the left/top properties(when given in %) are calculated based on height of the outer div(in your case, window).
But transform uses height/width of the element to determine translation, so you div will move left(50% width) and top(50% its height) since they are given in negatives, thus aligning it to the center of the page.
If you have to support older browsers(and sorry including IE9 as well) then the table cell is most popular method to use.
