package {
    import flash.display.Sprite;
    import flash.net.URLLoader;
    import flash.net.URLRequest;
    import flash.events.SecurityErrorEvent;

    public class SecurityErrorEventExample extends Sprite {
        public function SecurityErrorEventExample() {
            var loader:URLLoader = new URLLoader();
            loader.addEventListener(SecurityErrorEvent.SECURITY_ERROR, securityErrorHandler);

            var request:URLRequest = new URLRequest("http://www.[yourDomain].com");
            loader.load(request);
        }

        private function securityErrorHandler(event:SecurityErrorEvent):void {
            trace("securityErrorHandler: " + event);
        }
    }
}