When I tried to debug , I found that the document.getElementById('myswf.swf') returns null. But this is is the case with Firefox. I checked th js files and crossdomain.xml everthing is uploaded. The history folder is also uploaded.
Do I need to specify anything in crossdomain.xml apart from this?
<allow-access-from domain="*" secure="false" />
So you're resizing the Flash <object> in an HTML file? Is the object id="myswf.swf"? This is purely an HTML and JS activity, so the Flash policies have nothing to do with it.
Read up on allowScriptAccess