play object is cached, then the mask must be a
child of the display object. If an ancestor of the display object on the
display list is cached, then the mask must be a child of that ancestor or
one of its descendents. If more than one ancestor of the masked object is
cached, then the mask must be a descendent of the cached container closest
to the masked object in the display list.</p>
<p><strong>Note:</strong> A single <code>mask</code> object cannot be used to mask
more than one calling display object. Wh