1) Close the existing browser window and then open new instance of same browser. 2) Open new instance of different browser. 3)Use cookie less session. for this set cookieless="true" in web.config.

clear the session on logout execution use below line. hope its clears session value and id both Session.RemoveAll(); HttpContext.Current.Session.Clear(); HttpContext.Current.Session.Abandon(); HttpContext.Current.Response.Cookies.Add(new HttpCookie("ASP.NET_SessionId", "")); Response.Cache.SetCacheability(HttpCacheability.NoCache); Response.Cache.SetExpires(DateTime.UtcNow.AddHours(-1)); Response.Cache.SetNoStore(); Session.Clear(); Session.Abandon(); Response.Cookies["ASP.NET_SessionId"].Value = string.Empty; Response.Cookies["ASP.NET_SessionId"].Expires = DateTime.Now.AddMonths(-10);

you can use Abandon method of session.