Log Out Function in asp.net

Place it in Login form head section

<script type="text/javascript">

        function goback() {

            history.go(-1);

        }

    </script>

    <script type = "text/javascript" >

        function preventBack() { window.history.forward(); }

        setTimeout("preventBack()", 0);

        window.onunload = function() { null };

    </script>

on log out Click event

 Session.Abandon()

        FormsAuthentication.SignOut()

        Response.Cache.SetCacheability(HttpCacheability.NoCache)

        Response.Buffer = True

        Response.ExpiresAbsolute = DateTime.Now.AddDays(-1.0)

        Response.Expires = -1000

        Response.CacheControl = "no-cache"

        Response.Redirect("FrmLogin.aspx", True)