Please help me.. I am a beginner.. why does session does not get cleared and goes back in IE after signing out?

See more:

IE7

IE

session

I am a beginner and I am doing a project on shopping site. My logout code works on Firefox and Chrome but it does not really work on IE. Please help me solve this..

Here is my code..

protected void Page_Load(object sender, EventArgs e)
   {
       if (!Page.IsPostBack)
       {
           if (Session["admin_un"] != null)
           {
           }
           else if (Session["admin_un"] == null)
           {
               Response.Redirect("../Admin/AdminLogin.aspx");
           }
       }
   }

    public void sessionclear()
    {
        Session.Clear();
        FormsAuthentication.SignOut();
        string nextpage = "../Admin/AdminLogin.aspx";
        Response.Write("<script language=javascript>");
        Response.Write("{");
        Response.Write("var backlen=history.length;");
        Response.Write("history.go(-backlen);");
        Response.Write("window.location.href=" + nextpage + ";");
        Response.Write("}");
        Response.Write("</script>");
        Session["admin_un"] = null;
        Session.Abandon();
    }

    protected void lbtn_logout_Click1(object sender, EventArgs e)
    {
        sessionclear();
        Response.Redirect("../Admin/AdminLogin.aspx");
    }