Disable Browser back button in asp.net 2.0

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C#

ASP.NET

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

protected void Page_Load(object sender, EventArgs e)
   {

           Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "disableBackButton();", true);
       }

I have put this code in my page but after adding this page code is work but it is work for all the page of the website so i am not able to get back in the previous page.
I want to disable the back button just when user click on singout and enable for remaining all the pages