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 Jon Hoffman:
Is there someone you are mad or frustrated at, or even a sports team that you love to hate? Well now you can Flush It! Flush It is the first iPhone app that allows you to flush your frustration down the toilet. Simply select a picture from your photo gallery that represents who or what you are mad or frustrated with and swipe the toilet handle. Then you can watch your troubles go down the drain. You can even take a picture of the flush to save in your photo gallery or e-mail a snapshot of the flush. As a bonus, if you are extra frustrated with someone or something, press the icon of the little boy. We all know what he does. Flush It comes with great sound effects and animations. Its also a lot of fun at parties as a gag for your friends or to share your true opinion of someone.