I was getting that error, and my plugin is now working having followed two set of instructions. I don't know which of my actions resolved the issue, but here is what I did:
After following a set of about 10 steps that, sadly, I can not find the URL for, I got rid of the 102. Those particular instructions stated to add a "Canvas URL". This got rid of the 102, but gave me other errors— it produced a blurb in the "Facebook Publisher" box right of my post while in edit.
I then followed these instructions and wallah! it works. These instructions specify to go to your FB App page and click "Add to My Page". They also clarify which URL to add in the "Website URL" field of the App settings.
http://solutionsbyheidi.com/2011/10/10/using-simple-facebook-connect/
This is the way my app is currently setup and working. I hope you find it helpful:
Basic info
Display Name: This Useful App
Namespace: thisusefulapp
Contact: user@mydomain.com
App Domain: < this is empty >
Select how your app integrates with Facebook
Website
Site URL: http://myblogsdomain.com
App on FB
Canvas URL: http://apps.facebook.com/thisusefulapp/
Secure Canvas URL: https://apps.facebook.com/thisusefulapp/