Websites that have a shopping cart or checkout page, either using a known ecommerce platform or a custom solution.
cdnjs is a free distributed JS library delivery service.
Modernizr is a JavaScript library that detects the features available in a user's browser.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
PayPal is an online payments system that supports online money transfers and serves as an electronic alternative to traditional paper methods like checks and money orders.
PHP is a general-purpose scripting language used for web development.
Shopware is an enterprise-level ecommerce platform.
A modest JavaScript framework for the HTML you already have.