If I'm not mistaken, the Deep Discount DVD code(s) is/are only accepted during a designated 2-week period in June and November of each year. The code DD11 expired on November 19.
If you find something that you really like, you might want to go ahead and get it now; sometimes when they run out of certain dvds, they don't restock them. (I can never figure out which ones they'll get more of and which ones they won't.)