Answer: The only place where it is possible to disable the context menu attached to the right mouse button is from within the operating system - probably by editing the registry since I haven't seen any option to do it anywhere else. That assumes of course that the operating system is Windows. Other operating systems have different functionalitry attached to the right mouse button (if they have such a button).
No application such as a web browser should have any access to override this ofunctionality and will not have such access if security on the system is properly configured. JScript (on Internet Explorer) does allow this function to be blocked or replaced with a custom menu but this functionality is for use on intranets where the configuration of all computers accessing the site is known.
This article written by Stephen Chapman, Felgall Pty Ltd.