The #container element of this page has a min-height of 100%. That way, if the content requires more height than the viewport provides, the height of #content forces #container to become longer as well. Possible columns in #content can then be visualised with a background image on #container; divs are not table cells, and you don't need (or want) the fysical elements to create such a visual effect. If you're not yet convinced; think wobbly lines and gradients instead of straight lines and simple color schemes.
Because #container has a relative position, #footer will always remain at its bottom; since the min-height mentioned above does not prevent #container from scaling, this will work even if (or rather especially when) #content forces #container to become longer.
Since it is no longer in the normal flow, padding-bottom of #content now provides the space for the absolute #footer. This padding is included in the scrolled height by default, so that the footer will never overlap the above content.
Scale the text size a bit or resize your browser window to test this layout. The CSS file is over here.