Detect when the page doesn't load

[cameronjonesweb]

If the iframe has a height of 0px, then we know the page hasn't loaded properly. If an admin is logged in, then we should show a debug notice offering solutions.

1. Typos (see if we can hit up the Graph API with a request to see if the URL is valid)
2. Adblocker
3. Audience restrictions

Heineken is a good page to test with cause it has audience restrictions
Links to edit audience restrictions:
https://www.facebook.com/********/settings/?tab=settings&ref=page_edit&section=country_restrictions
https://www.facebook.com/********/settings/?tab=settings&ref=page_edit&section=age_restrictions