First, make sure to copy your View Cart button code in full directly from Seller Admin and paste at least one copy of that code into every page that has any number of Cart buttons. Your View Cart code is unique to you but the same for all your products, so it doesn't matter which product's button codes screen you copy it from. This code will add some javascript to your page that manages the overlay-style cart display "inside" your page.
However, once the buyer proceeds to checkout, with our service it is not possible to display the checkout screen itself within your own page. This help page explains the reasons for this limitation:
http://www.e-junkie.com/ej/faq.how.checkout.htm
You can at least upload a custom logo/header image to display on your E-junkie-generated checkout page for card-based payments; to upload this image, just log into your E-junkie Seller Admin, click Edit Profile, and use the Upload Your Logo button.
Our experience in evaluating iframe-embedded checkout methods has led us to conclude they would do more harm than good to your conversion rate. These methods depend on setting a cookie in the buyer's browser, which would be a "third-party" cookie because it's set for the domain of the payment processor's page inside the iframe, which would differ from the domain of your own page where the iframe is embedded. Most modern browsers allow users to block third-party cookies for privacy and security concerns, and some (including Safari and Firefox) lately block third-party cookies by default, so those users would be unable to use an iframe-embedded checkout at all.
