How to keep included footer at bottom of short page without min-height, sticky-footer or javascript

I've got 60 pages all with the same footer, included with php. The amount of content varies from 300px in height to 2000+. I don't think this is possible, but it would be great if I could get the footer to sit at the bottom of the browser window, if the page is shorter than the window, and behave normally (pushed to the bottom) otherwise, with just CSS. Thanks.