using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public partial class log_out : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        Response.Cache.SetExpires(DateTime.UtcNow.AddMinutes(-1));
        Response.Cache.SetCacheability(HttpCacheability.NoCache);
        Response.Cache.SetNoStore();  
    }
    protected void Timer1_Tick(object sender, EventArgs e)
    {
        string redirectUrl = FormsAuthentication.LoginUrl + "?ReturnUrl=log_in_form.aspx";
        FormsAuthentication.SignOut();



        ////FormsAuthentication.SignOut();
        //Session.Abandon();

        //// clear authentication cookie
        //HttpCookie cookie1 = new HttpCookie(FormsAuthentication.FormsCookieName, "");
        //cookie1.Expires = DateTime.Now.AddYears(-1);
        //Response.Cookies.Add(cookie1);

        //// clear session cookie (not necessary for your current problem but i would recommend you do it anyway)
        //HttpCookie cookie2 = new HttpCookie("ASP.NET_SessionId", "");
        //cookie2.Expires = DateTime.Now.AddYears(-1);
        //Response.Cookies.Add(cookie2);

        ////FormsAuthentication.RedirectToLoginPage();
        Response.Redirect(redirectUrl);  
    }
}