How do I extend a div background colour (or image) beyond the browser viewport?

Question

Hi there,
I have a web page, where I'm using onclick="showhide('ace'); to show an absolute positioned div ('ace') on top of the page, similar to a lightbox.
And like a lightbox, I am trying to add a transparent png between the div ace and the page.
Using the code below I can make it work. But when I scroll down the page, the background is cut short, determined by the browser size at the time of click.
Is there anyway to make it always fill the entire depth of screen even if the screen is resized, or there is scrolling?
Many thanks in advance!
#ace {
position: absolute;
top: 0px;
background:url(../images/fade.png) repeat-y;
z-index: 5;
width: 100%;
min-height:100%;
left: 0px;
#wrappercen, #containercen {
width: 954px;
padding-top: 75px;
#wrappercen {
top: 0px;
    right: 50%;
    position: absolute;
#containercen {
    left: 50%;
    position: relative;

Answer 1

True - although if you use display:none, and change it to display:block to show the div, it will only push the screen when it's being shown.  I'm not sure how the wizards do this in the lightboxy-things....