The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Scott Kehrberg:
Have you ever been in a store and picked out an item that was marked 25% off & also had a coupon for an additional 15% off? What is the final price? With the On Sale application, you simply type in the original price and the first and second discount percents. Tap the calculate button and you will instantly know the final price and how much you saved.No graphics to take up memory, just simple data entry and a quick calculation. On Sale will also allow you to find the sale price when only one discount is available. Just put 0 in for the second discount and away you go. A free iAd supported version is available. Please enter On Sale Lite in the search box.