vertically center full screen html-page in unknown screensize

[Hilholland]

Hey readers, I need some help.

I would like to open a website and this website is to be centered vertical in the browser window.

The html is coded to display full screen and I do not know the users screen size.
How do I make it vertically centered.

[Hilholland]

i have found a way;

http://www.wpdfd.com/editorial/thebox/deadcentre3.html