div tag in your form as a place holder for the iframe, which is created automatically later.
vindicia.setup() options, add lines as shown in this example:
setup() method is called, it creates an iframe. Notice the key shoesize. You can use this later if you want to validate this field.
When the fills out the form (enters a shoe size) and submits it, the shoe size is transmitted from the browser directly to Vindicia, and stored in your web session. It does not pass through your Web server.
Custom fields cannot contain credit card numbers at submit time. This is part of the automatic validation check. Also, a valid custom field is just a field that is not blank.

