Content Positioned in Y and X Middel : so I don't want my content positioned in middle along the X axis, I want the content in the middle of the Y axis to. 

In my CSS I've used the following to prevent the page becoming any bigger

    html { overflow-y: hidden; overflow-x: hidden }
and below is what I want to achieve. Just as an example, imagine a box in the middle. I believe this can be done with JavaScript, I'm just not sure how. 

[![Example Image][1]][1]

So the image above shows the box in the middle on both X and Y axis. **Please don't post how to position it in the middle along X Axis like this website as that's not what I woud like.** Any help will be awesome, thanks!

  [1]: http://i.stack.imgur.com/Y268i.png