javascript to trigger submit button click does not work on production server

I have javascript in content page, that calls javascript to trigger a button click when enter is pressed inside a textbox. the code works fine in my developement environment but does not work when published to production server. THis is the url of my production servr:  http://test.paperclipsetc.com/Account/Login




<script lang="javascript" type="text/javascript">

        function jftnSubmit(e) {

            if (e.keyCode == 13) {

                document.getElementById('<%= btnLogin.ClientID %>').click();
             }
             return false;
        }
         window.onload = function () {
            document.getElementById('<%= txtUserName.ClientID %>').focus();
        }
    </script>
 <input id="txtUserName" autofocus  runat="server" type="text"
                class="form-control" placeholder="Username" maxlength="50" onkeyup="return jftnSubmit(event); " />
<button id="btnLogin" runat="server" class="btn-standard"
                type="submit">
                Log In
            </button>