HTML5 is an emerging standard for writing web based apps.
HTML5 apps use a canvas element for graphics rendering. To change the size and layout of this canvas, you will need to modify the MonkeyGame.html and/or main.js files in the app's .build/html5 directory.
In order for an html app to make cross domain http requests (for example, using the HttpRequest class), the request server must be correctly configured.
More information can be found here: http://en.wikipedia.org/wiki/Cross-origin_resource_sharing
For example, you could use php to configure the server to send the following HTTP headers:
Access-Control-Allow-Headers: origin, content-type, access-control-allow-origin
Allow: GET, POST, OPTIONS