var newWindow

        function openWindow(URL, popW, popH) {
            ClosePopUpWindow();
            var w = 480, h = 340;
            if (document.all || document.layers) {
                w = screen.availWidth;
                h = screen.availHeight;
            }
            //var popW = 230, popH = 220;
            var leftPos = (w - popW) / 2, topPos = (h - popH) / 2;
            newWindow = window.open(URL, 'myNewWindow', 'toolbar=0, location=0, directories=0, status=0, menubar=0, scrollbars=1, resizable=0, width=' + popW + ',height=' + popH + ',top=' + topPos + ',left=' + leftPos);

        }

        function ClosePopUpWindow() {
            if (newWindow) {
                newWindow.close()
                newWindow = null
            }
        }