This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
This is definately a frequently asked question. There is no way to disable the back button. A much better approach is to make your web application happy to serve any of its pages based on the current state of its data model, and mark any dangerous pages as not to be cached.