var nav        = navigator.appName;
    var isIE       = nav == "Microsoft Internet Explorer";
    var isNetscape = nav == "Netscape";


    function DisableRbtn(button) {
        if (isIE) {
            event.returnValue = false;
            return false;
        }

        if (isNetscape) {
            if (button.which == 3)
                return false;
        }
    }


    if (isNetscape) {
        document.captureEvents(Event.MOUSEDOWN);
        document.captureEvents(Event.MOUSEUP);
    }

    document.onmousedown   = DisableRbtn;
    document.onmouseup     = DisableRbtn;
    document.oncontextmenu = DisableRbtn;