javascript issue in master page

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C#

ASP.NET

Javascript

In .aspx page i created one javascript function create like this

<%@ Page Title="" Language="C#" MasterPageFile="~/Menu.Master" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="LoupeMain.WebForm1" %>


<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server">

<script type="text/javascript">
    function disableBackButton() {
        window.history.forward();
    }
    setTimeout("disableBackButton()", 0);
    window.onunload = function () { null };

    </script>

</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
</asp:Content>

In .aspx.cs page i write like this code

protected void Page_Load(object sender, EventArgs e)
        {

            Response.AppendHeader("Refresh", Convert.ToString(((HttpContext.Current.Session.Timeout * 60) - 5)) + "; Url=" + "WebForm3.aspx");

        }

when after navigate the page the backward button of browser is not working
Why here javascript function is not working



Please give any suggetions for me