Logout or signout problem in asp.net c# using Master page and windows authentication

Login Page

protected void Page_Load(object sender, EventArgs e)
{
    Session["imp"] = "0";            
}

protected void LinkButton1_Click(object sender, EventArgs e)
{
    Session["imp"] = "1";
    Response.Redirect("AdminHome.aspx");
}

Log Out Page

protected void Page_Load(object sender, EventArgs e)
{
    Response.Cache.SetExpires(DateTime.UtcNow.AddMinutes(-1));
    Response.Cache.SetCacheability(HttpCacheability.NoCache);
    Response.Cache.SetNoStore();
    if (Session["imp"].ToString() == "1")
    { }
    else
    {
        Response.Redirect("HomePage.aspx");
    }  
}

protected void LinkButton1_Click(object sender, EventArgs e)
{
    Session["imp"] = "0";
    Session.Abandon();
    Response.Clear();
    Response.Redirect("HomePage.aspx");
}