function mouseDown(e)
{
   var shiftPressed=0;
   if (parseInt(navigator.appVersion)>3) {
   if (navigator.appName=="Netscape")
      shiftPressed=(e.modifiers-0>3);
   else 
      shiftPressed=event.shiftKey;
   if (shiftPressed)
   {
      alert ('Shift-click deshabilitado.')
      return false;
   }
}
 return true;
}


if (parseInt(navigator.appVersion)>3)
{
   document.onmousedown = mouseDown;
   if (navigator.appName=="Netscape") 
    document.captureEvents(Event.MOUSEDOWN);
}