Dom.Point and Region.contains, check if event occus in some div.

http://chunghe.googlecode.com/svn/trunk/experiment/yui.event/event.in.region.htm

  Event.on(document.body, 'click', function(e) {
    var xy = Event.getXY(e);
    var point = new YAHOO.util.Point(xy);
    var region = Dom.getRegion('foo');
    Dom.get('output').innerHTML = 'click inside? ' + '' + (region.contains(point)? 'true':'false') + '';
  });