I need to find whether the user clicking the browser back button or Refresh button.
I need to redirect the page to Error page when he clicks the back or refresh button. How to do this.
I need to do this in javascript for my ASP.net page
First of all, giving error messages if users use Back or have to refresh a page for whatever reason, is a really bad idea. Instead, you should transparently deal with that. Think about a page not coming up fully because of problems on the transportation level - the only option the user has is to reload or go back.
To answer your question, you have to keep track of the user's navigation yourself, that means on the server side. Forget about java-script here. If the user visits a website, you can store that information in a Session associated to the user (there are several methods of keeping these unique sessions, and I won't go into details here). If you store in your internal structures which pages the user visited lately, it is easy to determine a page being visited twice, or navigation going into the "wrong" direction.
You could easily generalize this (and making the whole thing more robust, for example against users jumping wildly between urls, or going back more than one step at once) by building a graph of "allowed" navigation and traversing it while the user is visiting websites.
The correct behaviour then if the user is doing a "wrong" navigation (like stepping back, reloading == visiting twice) is to get him back on track. Not to give an error message he can't escape! As he is not allowed to reload or go back, he has no options left.