...
The quickest test is to use the "Test" links that appear on the Dashboard Status page that is linked from your CF9 Splashpage (utilities).
Dashboard Status
...
The Test link on the left will follow the current DNS record. The Test link on the left will connect directly to the backend server. In a case where you are creating a new record or migrating from another host the right-hand link will be the one to test!
Testing DNS:
Testing backend:
For the truly techy savvy the "curl" command is a hint how you can test without using the Test links
...