On the web app page there are a couple links (about half way down the page) to the logs generated by your web app. They are access.log, error.log and server. They contain the following:
- access.log: contains logs of the which requests have reached the app, the response code and the time taken for the response to return
- error.log: contains all the errors generated by the web app. If your app isn't working as expected then this is probably the place to check first
- server.log: contains some production server logs and anything you've logged or printed in your app code