1 Create a project use flex sdk 3.4 2 Create a new mxml app Testadd.mxml 3 Add a source jpg Any.jpg content of Testadd.mxml just two line. [Embed(source="Any.jpg")] public var NotUsedSource:Class; I think this just defined a class which represent some data. And I never use it or initialize any instance of it in this app. 4 Profile this app, when it is profiling I click the resize button of IE servral times. 5 From the profiled data a function named Testadd_NotUsedSource.flash.events:IEventDispatcher:dispatchEvent is been called 6 My question is why this function has been called. I have the screenshot but can't add to this post.