If you add a custom script to the form and select the "submit data without reloading the page (AJAX)" checkbox, the form will process the following types of responses:
- {"message":"OK"} - successful data submission;
 - {"message":"Thank you for your submission"} - custom success message;
 - {"error":"This field … contains an error"} - custom failure message.
 
Alternatively, you can simply send back the submitted response or the HTML.