You cannot resize a scene from SWF, for example. to stage.stageWidth = 600;, but you can indicate that the HTML page changes the width / height properties of the embedded SWF, and then in SWF you can react to resizing the scene, for example.
stage.align = StageAlign.TOP_LEFT;
stage.scaleMode = StageScaleMode.NO_SCALE;
stage.addEventListener(Event.RESIZE, onStageResized, false, 0, true);
and update the layout from there.
If you change the size / elements in your HTML, this will change the size of the SWF stage.
SWF , , AS3 :
stage.scaleMode = StageScaleMode.NO_SCALE;
, SWF, .
, , , :
stage.align = StageAlign.TOP_LEFT;