In order to show correctly DWService content inside an IFrame, you have to include the following javascript library on your page:
<script src="https://www.apiremoteaccess.com/res/js/dwsapi.js" type="text/javascript">
</script>
This javascript code enables interaction between your application and DWService content. It works through the Cross-Domain Messaging (window.postMessage), so it’s important to set the property “postMessageOrigin” when you create a new session.