cdnjs is a free distributed JS library delivery service.
Google Analytics is a free web analytics service that tracks and reports website traffic.
Google Publisher Tag (GPT) is an ad tagging library for Google Ad Manager which is used to dynamically build ad requests.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
JSDelivr is a free public CDN for open-source projects. It can serve web files directly from the npm registry and GitHub repositories without any configuration.
Open Graph is a protocol that is used to integrate any web page into the social graph.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.