If you are using WIX, or any other website builder that only allows you to paste our Hosted Payments code inside an iFrame, please change the <form> tag to include a popup functionality.
One note: you will need to upgrade your site to a Premium package according to the terms of use for the Wix HTML Widget (see http://support.wix.com/index.php/The_Wix_Editor/HTML_Widget_Beta).
e.g.
<form method="post" action="https://www.payjunction.com/trinity/quickshop/add_to_cart.action">
becomes
<form method="post" target="_blank" action="https://www.payjunction.com/trinity/quickshop/add_to_cart.action">
Note: target = "_blank" has been added to the form tag.