I\'m trying to work my way through the Facebook tutorial publish and open graph story for iOS, https://developers.facebook.com/docs/tutorials/ios-sdk-tutorial/publish-open-graph
Error 100 means that there is a plain syntax error in the URL you are posting to.
I suspect you have a custom graph url set which doesn't match your action - see http://developers.facebook.com/docs/opengraph/creating-action-types :
Graph API URL This customizes the exact endpoint used when publishing actions, which by default for custom action types is /me/{app-namespace}:{action-type-name}.