Alexa Certified Site Metrics is an analytics service wich monitors and analyses web traffic and can be used to keep track of user behavior.
Authorize.net is a secure online payment gateway service that enables businesses to accept payments through various channels, such as ecommerce websites, mobile devices, and retail stores, providing a trusted platform for processing credit card and electronic cheque payments.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.