Apache is a free and open-source cross-platform web server software.
cdnjs is a free distributed JS library delivery service.
DoubleClick Ad Exchange is a real-time marketplace to buy and sell display advertising space.
Google AdSense is a program run by Google through which website publishers serve advertisements that are targeted to the site content and audience.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
YouTube is a video sharing service where users can create their own profile, upload videos, watch, like and comment on other videos.