右键失效

<script language="javascript">
   <!--
   if (window.Event)
  document.captureEvents(Event.MOUSEUP);
  function nocontextmenu()
  {
  event.cancelBubble = true
  event.returnValue = false;
  return false;
  }
  function norightclick(e)
  {
  if (window.Event)
  {
  if (e.which == 2 || e.which == 3)
  return false;
  }
  else
  if (event.button == 2 || event.button == 3)
 {
 event.cancelBubble = true
 event.returnValue = false;
 return false;
 }
 }
 document.oncontextmenu = nocontextmenu; //对ie5.0以上
 document.onmousedown = norightclick; //对其它浏览器
 //-->
 </script>
放在HEAD之间