Gravatar is a service for providing globally unique avatars.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
jQuery plugin for seeing if the images are loaded.
Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Redux Framework is a modular PHP library that allows developers to create customisable settings panels and controls for WordPress projects, providing a consistent user interface for managing options and settings.
Varnish is a reverse caching proxy.
WordPress is a free and open-source content management system written in PHP and paired with a MySQL or MariaDB database. Features include a plugin architecture and a template system.