A few subtests also concern Scalable Vector Graphics (SVG), Extensible Markup Language (XML), and data URIs.

[8] On browsers designed for personal computers, the animation has to be smooth (taking no more than 33 ms for each subtest on reference hardware equivalent to a top-of-the-line Apple laptop) as well,[9] though slower performance on a slow device does not imply non-conformance.

This tests that the web browser correctly handles the 404 error code when fetching the favicon, by treating this as a failure and displaying the generic icon instead.

After the Acid3 test page is completely rendered, the letter 'A' in the word "Acid3" can be clicked to see an alert (or shift-click for a new window) explaining exactly which subtests have failed and what the error message was.

This is required as the test uses a custom TrueType font, called "AcidAhemTest", to cover up a 20x20 red square.

Google employee Ian Hickson started working on the test in April 2007, but development progressed slowly.

In December 2007, work restarted and the project received public attention on 10 January 2008, when it was mentioned in blogs by Anne van Kesteren.

At the time, no browser using the Presto or WebKit layout engines passed the performance aspect of the test.

[29] Another Mozilla engineer, Boris Zbarsky, claimed that the subset of the specification implemented in Webkit and Opera gives no benefits to web authors or users over WOFF, and he asserted that implementing SVG Fonts fully in a web browser is hard because it was "not designed with integration with HTML in mind".

[30] On 2 April 2010, Ian Hickson made minor changes to the test after Mozilla, due to privacy concerns, altered the way Gecko handles the :visited pseudo-class.

[35] IE8 scored 20/100, which is much worse than all relevant competitors at the time of Acid3's release, and had some problems with rendering the Acid3 test page.

[36] Throughout 2010, several public Developer Previews improved Internet Explorer 9's test scores from 55/100 (on 16 March[37]) to 95/100 (as of 4 August).

Early iterations of the test were criticized for being a cherry-picked collection of features that were rarely used, as well as those that were still in a W3C working draft.

Limi argued that some of the tests, particularly those for SVG fonts, have no relation to real usage, and implementations in some browsers have been created solely for the point of raising scores.

In Hickson's words, Håkon Wium Lie from Opera Software and he commented out "the parts of the test that might get changed in the specs."

[45] Parts of the following standards are tested by Acid3: A passing score is only considered valid if the browser's default settings were used.