which event raise when we click back arrow button of web browser?

protected void Logout_Click(object sender, EventArgs e)
    {
        Session.Abandon();        
        FormsAuthentication.SignOut();
        Response.Cookies["TestCookies1"].Expires = DateTime.Now.AddYears(-1);
        Response.Cookies["TestCookies2"].Expires = DateTime.Now.AddYears(-1);
        Response.Redirect("~/login.aspx");
    }


Try this on logOut, It wud help u and still thr is same issue then
try this after writing upper portion. (its customized method of doing the same :) )
write a method on the load of masterpage

function GoBack() {
            if (document.cookie == "")
                document.location = '<%=HttpContext.Current.Request.ApplicationPath%>' + "/login.aspx";
        }

Don't forget to mark it as answer, if it works....