When was the last time there was a major shift away from backwards compatibility in HTML/CSS? I don't think there has been... has there? Yes; in the early 2000

When was the last time there was a major shift away from backwards compatibility in HTML/CSS? I don't think there has been... has there? Yes; in the early 2000’s, the W3C created XHTML 2.0 [1], a strict XML-based re-implementation of HTML. Because it dropped backwards compatibility to HTML4, it created a lot of backlash that (eventually) resulted in the browser vendors forming their own standards organization (WHATWG) which lead to the creation of HTML5. [1]: https://en.wikipedia.org/wiki/XHTML#XHTML_2.0 https://en.wikipedia.org/wiki/XHTML#XHTML_2.0