ACID2 test obsahuje schvalne chyby, aby se zjistilo, jak si prohlizec s nevalidnim kodem poradi ... je to napsano na http://www.webstandards.org/action/acid2/ : "Some 827 people (rough estimate, contents may have settled during shipping) have written to point out that the CSS used in the test is invalid. This is deliberate, as a means of exposing the ability of user agents to handle invalid CSS properly."