What is the difference between Firefox and IE on event binder

What is the difference between Firefox and IE on event binder

$j("#forwardcurveclose").bind("keypress",
    function(event) {
      alert('hello');
      var key = event.keyCode || event.which;
      if (key == 9) {
        .....;
      }
    }
  );

Upper code, working well under firefox, but never been triggered in IE8.  please let me know if you have any experiences with it, thanks.