gwt application using facebook login local testing

Hi,

I am developing a gwt web application and testing it locally. I provide an option of login by facebook account.

The URL to test locally is http://127.0.0.1:8888/TestFB.html?gwt.codesvr=127.0.0.1:9997.

What should I put in,

FB developer->Apps->"App name"->"Website with Facebook Login"->Site URL ?

Thanks