As Stevie D said above the faux column goes on a parent of the floated element (preferably not on the body though as that is always one pixel out on some browsers).
The parent holds the floats and therefore is always as tall as the tallest float and therefore an image repeated on the parent will always reach the bottom and make both columns appear to be equal. The actual columns don't change their height but that doesn't matter as they just lay on to p of the background.
More info here.
Your site is showing as an "atttack site" so you need to make sure all malware has been removed and then probably re-submit it to google (go to webmaster tools and
select request a review once you have cleaned the site ).