.....

<script language="JavaScript">
<!--
function mouseDown(e) {
var ctrlPressed=0;
var altPressed=0;
var shiftPressed=0;
if (parseInt(navigator.appVersion)>3) {
  if (navigator.appName=="Netscape") {
   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=event.shiftKey;
   altPressed  =event.altKey;
   ctrlPressed =event.ctrlKey;
   self.status=""
    +  "shiftKey="+event.shiftKey
    +", altKey="  +event.altKey
    +", ctrlKey=" +event.ctrlKey
  }
  if (shiftPressed || altPressed || ctrlPressed)
   alert ("Mouse clicked with the following keys:n"
    + (shiftPressed ? "Shift ":"")
    + (altPressed   ? "Alt "  :"")
    + (ctrlPressed  ? "Ctrl " :"")
   )
}
return true;
}
if (parseInt(navigator.appVersion)>3) {
document.onmousedown = mouseDown;
if (navigator.appName=="Netscape")
  document.captureEvents(Event.MOUSEDOWN);
}
//-->
</script>