Why? Acid3 just requires basic CSS support and a someone ES5 conformant js-implementation. Acid2 was specifically built to call IE out and to put browser build

Why? Acid3 just requires basic CSS support and a someone ES5 conformant js-implementation. Acid2 was specifically built to call IE out and to put browser builders on notice. It tests the most nuanced little quirks of some specific specs; and, because of some changes in the modern standard, doesn’t actually conform anymore.