if (document.all) {
    //IE 5.+
    document.oncontextmenu = function () {
    return false;
    };
    document.onkeydown = function () {
    //alert("onKeyDown: " + window.event.keyCode + "\nsrcElement: " + window.event.srcElement.tagName);
      if ((window.event.keyCode == 78 && window.event.ctrlKey == true) || window.event.keyCode == 93) {
        window.event.keyCode = 0;
        window.event.cancelBubble = true;
        window.event.returnValue = false;
        return false;
        }
    };
  } else if (document.layers) {
    //NS 4.x
    document.captureEvents(Event.MOUSEDOWN);
    document.onmousedown = function (evt) {
      if (evt.which == 3) 
      return false;
    };
  } else if (parseInt(navigator.appVersion) >= 5 && navigator.appName == "Netscape") {
    //NS 6.+
    document.onmouseup = function (evt) {
      if (evt.button == 3)
      event.preventDefault();
    }
  }