World Wide Web Consortium (W3C) standards define the best practices for web development to enable developers to build rich interactive experiences that are available on any device. Theses standards range from recommended web technologies such as HTML, CSS, XML to the generally accepted principles of web architecture, semantics and services.
Web Hypertext Application Technology Working Group (WHATWG) is another set of web standards that came into existence after W3C announced that it was going to be focusing on XHTML over HTML.
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