cdnjs is a free distributed JS library delivery service.
Cloudflare Browser Insights is a tool that measures the performance of websites from the perspective of users.
Cloudflare is a web-infrastructure and website-security company, providing content-delivery-network services, DDoS mitigation, Internet security, and distributed domain-name-server services.
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.
Modernizr is a JavaScript library that detects the features available in a user's browser.