How to disable browser\'s BACK Button (across browsers)?
There have been a few different implementations. There is a flash solution and some iframe/frame solutions for IE. Check out this
http://www.contentwithstyle.co.uk/content/fixing-the-back-button-and-enabling-bookmarking-for-ajax-apps
BTW: There are plenty of valid reasons to disable (or at least prevent 1 step) a back button -- look at gmail as an example which implements the hash solution discussed in the above article.
Google "how ajax broke the back button" and you'll find plenty of articles on user testing and the validity of disabling the back button.