Getting a DIV to cover a whole PAGE instead of just the SCREEN

Hi;

I was coding my first "light box" effect when I found out that the div
that I was using to gray out my page only covered the screen revealed
by the brower, not the whole HTML page.

I got around this with the javascript hack of setting the div height
to be the document height.

I heard that javascript is not necessary, that if the HTML & document
style height are set to 100% the problem will not exist.

That didn't work for me.

Can anyone provide me with an example?

The less script I use the happier I am.

Steve