How do I disable Back button on the browser?

Question

I would like to disable the back button on the browser.  I have done it before using this code on the page load, but for some reason it is not working anymore.

        Response.Cache.SetCacheability(HttpCacheability.NoCache)

the application that I am running it is actually running as an iFrame for a second application, I wondering if this is the reason my code it is not working.