Have you created an app with Facebook over at developer.facebook.com and entered your app ID and secret keys into your script?
Also don't forget to change your URL from test to development server - I've been caught out with that once
Edit
It looks like you've just copied and pasted the output HTML by right-clicking and going to view source. This isn't the same as on run time, the snippet will be created with some more information.
Hunt down the code in the generating file and use that instead