API Error Code: 100

Jun 7, 2010 at 4:18 PM

I have downloaded the start kit and am trying to get the Iframe sample working - I have followed all the instructions and changed the api key etc... But as soon as I browse to my app on facebook I get the following error?

> API Error Code: 100
> API Error Description: Invalid parameter
> Error Message: Requires valid next URL.

Anyone else had this problem?  I'm struggling to find an answer to what the error actually means?