I am developing a card payment page using Realex Payments’ HPP API with an iFrame for hosting the Realex page. On the Realex request form I have the fields HPP_POST_DIMENSIONS and HPP_POST_RESPONSE set to my URL as follows: Payment page: www.example.com/account/payment.html The hidden field values are used to post back data from Realex, using event listeners, to my page when