[|up vote]87[|down vote]accepted
UPDATE:
To answer the API Error Code: 191
The -+redirect_uri+- should be equal (or relative) to the Site URL.
Tip: Use base URLs instead of full URLs pointing to specific pages.
NOT RECOMMENDED: For example, if you use -+www.mydomain.com/fb/test.html+- as your Site URL and having -+www.mydomain.com/fb/secondPage.html+- as -+redirect_uri+- this will give you the 191 error.
RECOMMENDED: So instead have your Site URL set to a base URL like: -+www.mydomain.com/+- OR -+www.mydomain.com/fb/+-.
https://stackoverflow.com/questions/4691782/facebook-api-error-191
A Refresh Token is a special kind of token that can be used to obtain a renewed access token —that allows accessing a protected resource— at any time. ...Refresh tokens must be stored securely by an application because they essentially allow a user to remain authenticated forever.