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, this will position your application in the top left of your page.
You can't really act on the page's size though, as it depends on the browser and the resolution of the user.
I have a screen resolution of 1920X1080, and my browser is always amximised, there's no way I will have a webpage of 728X90.
But, you can set your application size (project properties) to be at the exact size you want. You are sure this way that your application will never be bigger than the size you want. (especially if you don't use the fullscreen properties)
Also, I'm not sure if placing the game in an iFrame will work smootlhy as expected. Nothing else to do here but try.