Interdire le clic du milieu en javascript

<script language="JavaScript">
<!--
function mouseDown(e) {
 var ctrlPressed=0;
 var altPressed=0;
 var shiftPressed=0;
 
 if (parseInt(navigator.appVersion)>3) {

  var evt = navigator.appName=="Netscape" ? e:event;  
  if (navigator.appName=="Netscape" && parseInt(navigator.appVersion)==4) {
   
   var mString =(e.modifiers+32).toString(2).substring(3,6);
   shiftPressed=(mString.charAt(0)=="1");
   ctrlPressed =(mString.charAt(1)=="1");
   altPressed  =(mString.charAt(2)=="1");
   self.status="modifiers="+e.modifiers+" ("+mString+")"
  }
  else {
   
   shiftPressed=evt.shiftKey;
   altPressed  =evt.altKey;
   ctrlPressed =evt.ctrlKey;
   self.status=""
    +  "shiftKey="+shiftPressed 
    +", altKey="  +altPressed 
    +", ctrlKey=" +ctrlPressed 
  }
  if (shiftPressed || altPressed || ctrlPressed) 
alert ('~ Commande interdite sur Team Networks ~')
}
 return false;
 }
if (parseInt(navigator.appVersion)>3) {
 document.onmousedown = mouseDown;
 if (navigator.appName=="Netscape") 
  document.captureEvents(Event.MOUSEDOWN);
}
//-->
</script>