In this video I have shown step by step how you can solve the below facebook APP error,
Can't Load URL: The domain of this URL isn't included in the app's domains. To be able to load this URL, add all domains and subdomains of your app to the App Domains field in your app settings.
Here is the steps you have to follow for Solving the Error.
1. Open the Facebook App page from Facebook developer page.
2. Open Settings >> Basic Settings
3. Add the platform as Website.
4. Enter the Site URL as shown in the Image
5. Add the App Domain as shown
6. Now Refresh the page and Run the Facebook page. It will work without any error.