ASp.net page caching problem

[c83]

after a user makes

FormsAuthentication.SignOut();
  Response.Redirect('login.aspx');

it is redirected to the login page.
But if in the browser it pushes the Back button the last visited page is shown.
i added this in the Global.asax file in the BeginRequest:

HttpContext.Current.Response.Cache.SetExpires(DateTime.Now.AddSeconds(-1));
 HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);

and even tried adding custom HTTPHeaders in IIS: pragma:no-cache; cache-control:no-cache; expires:-1;
and i must say that this is working in Internet Explorer( when user presses Back button it is redirected to the login page), but not working in Opera and Firefox.
How to handle this situation??

[c83]

And i forgot, i also added this:

<%@ OutputCache Duration="1" VaryByParam="none"%>