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You cannot display a lot of websites inside an iFrame. Reason being that they send an "X-Frame-Options: SAMEORIGIN" response header. This option prevents the browser from displaying iFrames that are not hosted on the same domain as the parent page. This is a security feature to prevent click-jacking. Some details at How to show google.com in an iframe?
This could be of some help : https://www.maketecheasier.com/create-survey-form-with-google-docs/