URL encoding for Facebook page tabs and canvas pages
It is important to URLencode your canvas and page tab URLs so as to not receive Facebook API 191 error messages.
For example in creating Facebook page tabs:
https://www.facebook.com/dialog/pagetab?app_id=YOUR_APP_ID&next=https%3a%2f%2fYOUR_APP_URL.com%2f
Otherwise you’ll keep getting this error message:
“API Error Code: 191 API Error Description: The specified URL is not owned by the application Error Message: Invalid redirect_uri: Given URL is not allowed by the Application configuration.”