codice:
<HTML>
 <HEAD>
 <script>
function on_MouseMove(e) {
  if (!e) var e = window.event;
  (x = e.x) ? x : e.pageX;
  (y = e.y) ? y : e.pageY;
  document.getElementById("pos").value = "x: " + x + " | y: " + y;
  }
</script>
 </HEAD>

 <BODY>
 <div style="border:1px solid red;width:300px;height:300px;position:relative;" onmousemove="on_MouseMove()" "mm('pippo')">.</div>
 <input type="text" id="pos">
 </BODY>
</HTML>
Prova questo, io qui non ho firefox.

ciao