Cloudflare is a web-infrastructure and website-security company, providing content-delivery-network services, DDoS mitigation, Internet security, and distributed domain-name-server services.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
MkDocs is a static site generator, used for building project documentation.
Open Graph is a protocol that is used to integrate any web page into the social graph.