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.
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.
PHP is a general-purpose scripting language used for web development.
SweetAlert is a JavaScript library that provides alternative alert and modal dialog boxes for web applications, with customisable features, aiming to improve the user interface of the default browser dialogs.
Typekit is an online service which offers a subscription library of fonts.