W3c is the body that attempts to standardize these items, they create the rules, then programmers create their rendering motor to interpret those principles. It's not at all similar to "all td, th and caption features which happen to be contained by a div element with a class of test". https://www.presta-addons-modules.com/en/free-modules/prestashop-preloader-page-loading-image-page-loading-animation-preloading-screen-loading-page.html