Chained Dropdowns using AJAX

Countries and States
The states list is updated each time the country is switched. It also has a basic fallback for POST data (will auto-remember the previous selection).
Also note how "Please select" requires input, whereas "No option available" does not.

Submit the form to see how validation kicks in and how it behaves with these two different options (required vs. no option available).

Send your feedback or bugreport!