cdnjs is a free distributed JS library delivery service.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
jQuery is a JavaScript library which is a free, open-source software designed to simplify HTML DOM tree traversal and manipulation, as well as event handling, CSS animation, and Ajax.
Modernizr is a JavaScript library that detects the features available in a user's browser.
Open Graph is a protocol that is used to integrate any web page into the social graph.
WhatsApp Business is a free to download app available on Android and iPhone using which businesses can connect with their customers.