This Error is because you had not provided API Keys while embed Google Map.
If you are using the standard Google Map JavaScript API, you must use a key parameter with a valid API key. If you are a Premium Plan customer, you must use either a client parameter with your client ID or a key parameter with a valid API key.
Getting API Keys - https://developers.google.com/maps/documentation/javascript/get-api-key
To Debug Such JS Error
Use Chrome, IE or Firefox and Press F12, to check error log.