Setting page div to height of browser window in zen-fixed?

I am trying to set the page div at 100% the height of the browser window so the footer is on the bottom and the left and right borders I have created for the page div extend to the bottom. I am using the zen-fixed theme, which is a subfile within the zen theme. I have tried min-height: 100% and height: 100% in the style rules for #page on each of the three style sheets where it appears with no effect. Can someone tell me how to do this? Thank you.