How to show session timeout warning popup for complete application

Question

I want to create session timeout warning popup with timer.

I have included code in master page and it working well just for master page, when i open any page which is link with master then session time start but i want for complete application.

Master page aspx

<script>
  function SessionExpireAlert(timeout) {
            var seconds = timeout / 1000;
            document.getElementsByName("secondsIdle").innerHTML = seconds;
            document.getElementsByName("seconds").innerHTML = seconds;
            setInterval(function () {
                seconds--;
                document.getElementById("seconds").innerHTML = seconds;
                document.getElementById("secondsIdle").innerHTML = seconds;
            }, 1000);
            setTimeout(function () {
                //Show Popup before 20 seconds of timeout.
                $find("mpeTimeout").show();
            }, timeout - 20 * 1000);
            setTimeout(function () {
                window.location.href = "/WebForm5.aspx";
            }, timeout);
            return false;
        };
        function ResetSession() {
            //Redirect to refresh Session.
            window.location = "/WebForm5.aspx";
        }
</script>

<form runat="server" novalidate="" role="form"  class="form-horizontal">
                   <asp:LinkButton ID="lnkFake" runat="server"/>
                   <asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
                   <asp:ModalPopupExtender ID="mpeTimeout" BehaviorID="mpeTimeout" runat="server" 
         PopupControlID="pnlPopup" TargetControlID="lnkFake" OkControlID="btnYes" CancelControlID="btnNo" BackgroundCssClass="modalBackground" OnOkScript="ResetSession()">

    </asp:ModalPopupExtender>
        <asp:Panel ID="pnlPopup" runat="server" CssClass="modalPopup" Style="text-align: center" BorderColor="#cee2e5" BorderStyle="Solid" BackColor="white" class="header">

            <asp:Label ID="Label1"  runat="server" BackColor="#cee2e5" Font-Bold="True" Text="Session Expiry Alert" Font-Size="Large" ForeColor="DarkBlue" Style="margin-top: 0px" Width="363px" Visible="true"></asp:Label>
          <br />
             <asp:Label ID="Label2" runat="server" style="color:black;font-size:16px;" Text="Your Session will expire in"></asp:Label><span style="color:red;font-size:20px;" id="seconds"></span> <asp:Label ID="Label3" runat="server" style="color:black;font-size:16px;" Text=" Seconds"></asp:Label>
            <br />
            <div class="footer">
                <asp:Button ID="btnYes" runat="server" BackColor="Red" ForeColor="White" BorderColor="White" BorderWidth="1px" Text="Logoff" CssClass="yes" />
                <asp:Button ID="btnNo" runat="server" BackColor="Green" BorderColor="White" ForeColor="White" BorderWidth="1px" Text="Continue" CssClass="no" />
            </div>


        </asp:Panel>

           <asp:ContentPlaceHolder ID="body" runat="server">
          </asp:ContentPlaceHolder>
                  </form>

aspx.cs

 protected void Page_Load(object sender, EventArgs e)
        {
            Response.Cache.SetCacheability(HttpCacheability.NoCache);

                if (!IsPostBack)
                {
                    Session["Reset"] = true;
                    Configuration config = WebConfigurationManager.OpenWebConfiguration("~/Web.Config");
                    SessionStateSection section = (SessionStateSection)config.GetSection("system.web/sessionState");
                    int timeout = (int)section.Timeout.TotalMinutes * 1000; //I change the timeout value to 25 seconds
                    Page.ClientScript.RegisterStartupScript(this.GetType(), "SessionAlert", "SessionExpireAlert(" + timeout + ");", true);
                }  
        }

I want when session expire on any page on application then session timeout warning popup will be show.