title: Convert IE event.button to W3C event.button
body: <p>On mouse-down (and up) I need to check which mouse button has changed its state. This is pretty easy with the W3C model and even the old netscape way (event.which) but IE gives me a headache. I know that event.button in IE is a bitmask but the problem is that I can't find out which button was pressed from this bitmask. If IE gives me event.button == 3 then I can't tell if the user pressed the left button while the right button was already down or if the user pressed the right button while the left button was already down.</p>
  
  <p>To solve this problem once and for all I'm searching for a nice generic solution to convert the broken IE event into a W3C compatible event. Maybe someone already did that and wants to share?</p>