I’ve seen many affiliates place affiliate links & banners in the footer or near the bottom of their pages and wanted to emphasize that these links have the lowest click-through rates.
Since the great majority of web surfers focuses on what they see on their screen, without scrolling down, it is most likely that nobody – except you -- will ever see these links at the bottom of your pages. In this case don’t be surprised if you never make any sale, which you can’t blame on the affiliate programs you promote.
Put instead your affiliate links in heat zones such as the header, navigation, columns and top-right body if you want to make some sales.