1. Go to http://www.alexa.com 2. Search for "thank you for ordering" 3. Check out the search results. I read this on a blog the other week, and it speaks volumes for the time and care that has been put in to these sites! Alexa is not built in the same way as Google. It doesn't prevent your order confirmation pages from displaying. Something to keep in mind if you're offering a digital product!
There is a way to protect digital products on the Internet. Either using DLGuard or using cheap one like e-junkie. This way, the download page will be protected. Not many using it and that's why they keep losing their money due to people download their products for free.