Question: Can we block the back button on the browser so that if we click on back button it is ignored?
Answer: For security reasons client side processing is restricted to accessing only the content of the web page and cookies set by the site. The back button is part of the browser and is therefore not allowed to be messed with. There may be one or more browsers with an unplugged security hole that allows such access but any sensible person would not run a browser that allowed that level of access to their computer.
This article written by Stephen Chapman, Felgall Pty Ltd.