Acid2 is a test page published and promoted by the Web Standards Project to expose web page rendering flaws in web browsers and other applications that render HTML. It was developed in the spirit of Acid1, a relatively narrow test of compliance with the Cascading Style Sheets 1.0 (CSS1) standard, and was released on April 13, 2005. Like Acid1, a web browser passes the test if the way it renders the test page matches a reference rendering.
Acid2 tests aspects of HTML markup, CSS 2.1 styling, PNG images, and data URIs. It should render correctly on any application that follows the World Wide Web Consortium and Internet Engineering Task Force specifications for these technologies. The idea is that if both web sites and web browsers follow agreed-upon industry standards, then any web site will work the same in any web browser.
On October 31, 2005, Safari 2.0.2 became the first browser to pass the test. Opera, Konqueror, Firefox, and others followed. The only major browser that does not yet pass the test is Internet Explorer, although a version of Internet Explorer that passes Acid2 is in development.
