Application container with no padding lets its child VBox container fill the entire window
<?xml version="1.0"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" width="100" height="100" paddingTop="0" paddingBottom="0" paddingLeft="0" paddingRight="0"> <mx:VBox width="100" height="100" backgroundColor="#A9C0E7"> </mx:VBox> </mx:Application>