Note that some of the fields for the checkout page is only applicable for the older styled PayPal checkout page. View the tooltips to determine if the field is applicable or not to the new checkout page.
Default IPN URL - This can be used to pre-populate a new button's Instant Payment Notification URL which is useful if you are using your own IPN script. Leave it blank if you are using EzPPb's Payment Tracking feature. IPN URLs can be overridden in individual buttons.