ASP .Net Windows Authentication

If you use Windows Authentication, and the user is not allowed to access the specific page, a nasty 401.2 Access Denied error message will be displayed to the user. What if you want to display a friendly error message?

You would think that an entry in the <customErrors> section would work? No, it does not.

To get to the solution: You have to define Application_EndRequest in Global.asax.cs that looks something like

    protected void Application_EndRequest(object sender, EventArgs e)
    {
        HttpContext context = HttpContext.Current;
        if (context.Response.Status.Substring(0,3).Equals("401"))
        {
        context.Response.ClearContent();
        context.Response.Write("<script language="javascript">" +
                       "self.location='NotAllowed.aspx';</script>");
        }
    }

Then you create the NotAllowed.aspx page to display a nice friendly message to the user.

You can find more information here.