Acid2

Infobox Website
name = Acid2



caption = This is the reference image for Acid2. In the real test, the nose becomes blue while the cursor is hovering over it.
url = [http://acid2.acidtests.org/ acid2.acidtests.org]
commercial =
type = Web standards test
language =
registration =
owner = The Web Standards Project
author = Ian Hickson
launch date = April 12, 2005
current status =
revenue =
slogan =

Acid2 is a test page published and promoted by the Web Standards Project to identify 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 (CSS) standard, and was released on April 12, 2005. Like Acid1, the way a web browser renders the test is compared to a reference rendering. If the two match, the browser is considered to pass the test.

Acid2 tests aspects of HTML markup, CSS 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 an Acid2-compliant version of the browser is in development.

Name

Acid2 is a short for "Acid test #2". During the the gold rush of the 1850s, an acid test was a test designed to testify weather a given (excavated or found) metal is indeed gold.

Acid test was "the" test of the time, since it was decisive, immediate, cheap and extremely simple to perform. An analogy is drawn from this historical test to the modern test - if a browser passes the acid test it is approved, very much in the same manner that if a metal passes the acid test it is accepted.

History

[
Ian Hickson, the author of the test]

Acid2 is the brainchild of Håkon Wium Lie, chief technical officer of Opera Software and creator of the widely-used Cascading Style Sheets web standard. [cite web
url=http://www.root.cz/texty/hakon-wium-lie-css-was-created-to-save-html/
title=Håkon Wium Lie: CSS was created to save HTML
last=Hassman
first=Martin
date=2008-05-12
accessdate=2008-07-27] Together with a colleague, Ian Hickson, he created the first draft of Acid2 in February 2005.cite web
url=http://ln.hixie.ch/?start=1137799947&count=1
title=People who don't realise that they're wrong
last=Hickson
first=Ian
work=Hixie's Natural Log
date=2006-01-20
accessdate=2008-04-01] Acid2 was first publicly announced on March 16, 2005 in a CNET article where Lie challenged Microsoft to design Internet Explorer 7, then in development, to pass the test.cite web
url=http://news.cnet.com/The-Acid2-challenge-to-Microsoft/2010-1032_3-5618723.html
title=The Acid2 challenge to Microsoft
author=Lie, Håkon Wium
authorlink=Håkon Wium Lie
publisher=CNET Networks
date=2005-03-16
accessdate=2008-01-12]

Ian Hickson coded the actual test in collaboration with the Web Standards Project and the larger web community. [cite web
url=http://www.webstandards.org/about/members/hixie/
title=Ian Hickson
publisher=The Web Standards Project
accessdate=2008-03-25] [cite web
url=http://www.webstandards.org/about/members/bhenick/
title=Ben Henick
publisher=The Web Standards Project
accessdate=2008-04-02] [cite web
url=http://www.webstandards.org/about/members/dbaron/
title=David Baron
publisher=The Web Standards Project
accessdate=2008-04-02] It was officially released on April 13, 2005 [cite press release
url=http://www.webstandards.org/press/releases/20050413/
title=Acid2: Putting Browser Makers on Notice
publisher=The Web Standards Project
date=2005-04-13
accessdate=2008-04-01] and at that time, every web browser failed it spectacularly.cite web
url=http://weblogs.mozillazine.org/hyatt/archives/2005_04.html#007932
title=The Acid2 Test
last=Hyatt
first=Dave
work=Surfin' Safari
publisher=MozillaZine
date=2005-04-12
accessdate=2008-04-01]

In July 2005, Chris Wilson, the Internet Explorer Platform Architect responded by calling Acid2 a "wish list" of features and said that while the test was important to Microsoft, Acid2 compliance was not a priority for Internet Explorer 7. [cite web
url=http://blogs.msdn.com/ie/archive/2005/07/29/445242.aspx
title=Standards and CSS in IE
last=Wilson
first=Chris
work=IEBlog
publisher=Microsoft
date=2005-07-29
accessdate=2008-03-11] Microsoft later joined other browser makers and Internet Explorer 8 is expected to pass the test.cite web
url=http://blogs.msdn.com/ie/archive/2007/12/19/internet-explorer-8-and-acid2-a-milestone.aspx
title=Internet Explorer 8 and Acid2: A Milestone
last=Hachamovitch
first=Dean
work=IEBlog
publisher=Microsoft
date=2007-12-19
accessdate=2008-03-09]

On April 23, 2005, Acid2 was updated to fix a bug that made the mouth appear too close to the nose. [cite web
url=http://weblogs.mozillazine.org/hyatt/archives/2005_04.html#008011
title=Acid2: Version 1.1 Posted
work=Surfin' Safari
last=Hyatt
first=Dave
publsher=MozillaZine
date=2005-04-23
accessdate=2007-12-24] [cite web
url=http://weblogs.mozillazine.org/hyatt/archives/2005_04.html#007977
title=Acid2: Lopping Off the Sideburns
work=Surfin' Safari
last=Hyatt
first=Dave
publsher=MozillaZine
date=2005-04-20
accessdate=2008-05-14] After several complaints, the test was again updated in January 2006 to remove a test for unpopular SGML-style comments that were never widely implemented.

In March 2008, Ian Hickon released Acid3 as a follow-up to Acid2. While Acid2 primarily tests CSS, Acid3 focuses more on JavaScript and other "Web 2.0" technologies. [cite web
url=http://www.webstandards.org/action/acid3/
title=Acid3 Browser Test
publisher=The Web Standards Project
accessdate=2008-08-15]

Overview of standards tested

Acid2 tests a variety of web standards published by the World Wide Web Consortium and the Internet Engineering Task Force. All web standards tested were codified before the year 2000. [cite press release
url=http://www.w3.org/Press/PNG-PR.en.html
title=World Wide Web Consortium Issues First Recommendation for PNG
publisher=World Wide Web Consortium
date=1996-10-07
accessdate=2008-08-12] [cite web
url=http://www.w3.org/TR/REC-CSS2/
title=Cascading Style Sheets, Level 2
publisher=World Wide Web Consortium
date=1998-05-12
accessdate=2008-08-12] cite web
url=http://tools.ietf.org/html/rfc2397
title=RFC 2397 - The "data" URL scheme
publisher=Internet Engineering Task Force
month=August
year=1998
accessdate=2008-08-12] [cite web
url=http://www.w3.org/TR/REC-html40/
title=HTML 4.01 Specification
date=1999-12-24
accessdate=2008-08-11] Specifically, Acid2 tests:cite web
url=http://www.webstandards.org/action/acid2/guide/
title=Acid2: The Guided Tour
publisher=The Web Standards Project
accessdate=2007-12-24]

* Alpha transparency in PNG-format
The eyes of the smiley face use "alpha transparency" which is part of the 1996 Portable Network Graphics specification. The alpha transparency provides an elegant way to have the eyebrows smoothly blend into the face. This was a significant issue because Internet Explorer 6, the most widely used web browser at the time Acid2 was released, [cite web
url=http://www.thecounter.com/stats/2005/April/browser.php
title=Browser Stats
publisher=TheCounter.com
month=April
year=2005
accessdate=2008-08-23] did not support alpha transparency. This deficiency was rectified in Internet Explorer 7, bringing Internet Explorer in line with other web browsers in this regard. [cite web
url=http://www.howtocreate.co.uk/alpha.html
title=Making IE use PNG Alpha transparency
author=Wilton-Jones, Mark "Tarquin"
accessdate=2008-07-31]

* The object element: The eyes also test support of the HTML object element. The object element has been a part of HTML since HTML 4 was released in 1998, [cite web
url=http://www.w3.org/TR/1998/REC-html40-19980424/
title=HTML 4.0 Specification
publisher=World Wide Web Consortium
date=1998-04-24
accessdate=2008-07-28] yet by 2005 it still was not completely supported in all web browsers. The creators of Acid2 considered object element support important because it allows for content fallback; in other words, if the specified object fails to load then alternative (generally simpler, more reliable) content can be presented instead.

* data URIs: The actual images that form the eyes are encoded as data URIs. Data URIs allow embedding multimedia directly into web pages rather than being stored as a separate file. Acid2 tests the most common case, where a binary image is base64-encoded into text and then that encoded text is included in a data URI in the web page. Interestingly, although the specification for data URIs was published in 1998, it was never formally adopted as a web standard. Nonetheless, the data URI scheme has become a "de facto" web standard implemented by most browsers.

* Absolute, relative, and fixed CSS positioning: Absolute positioning means that the web developer specifies the exact X and Y coordinates where an element is to be placed into the page. Relative positioning means that the web developer specifies an X and Y offset from the usual position of the element. Fixed positioning means that the element is placed relative to the browser window, and scrolls with the window rather than with the rest of the page. [cite web
url=http://kilianvalkhof.com/2008/css-xhtml/understanding-css-positioning-part-1/
title=Understanding CSS Positioning part 1
last=Valkhof
first=Kilian
date=2008-05-05
accessdate=2008-07-31]

* The CSS box model: This feature allows specifying dimensions, padding, borders, and margins, [cite web
url=http://www.w3.org/TR/REC-CSS2/box.html
title=Box model
work=Cascading Style Sheets, level 2
publisher=World Wide Web Consortium
date=1998-05-12
accessdate=2007-07-30] and was the focus of the original Acid1 test. Acid2 not only retests margin support but also tests minimum and maximum heights and widths, features new to CSS 2.0.

* CSS table formatting: This part of CSS allows applying table formatting without traditional HTML table markup.

* CSS generated content: Using CSS generated content, web developers can add decorations and annotations to specified elements without having to add the content to each one individually.

* CSS parsing: A number of illegal CSS statements are present in Acid2 to test error handling. Standards-compliant browsers are expected to handle these errors as the CSS specification directs. This helps ensure cross-browser compatibility by making all browsers treat CSS with the same level of strictness, so that what works in one browser should not cause errors in another.

* Paint order: Acid2 requires that the browser have standard paint order, that is, overlapping elements should be placed or "painted" on top of each other in the correct order.

* Hovering effects: When the user moves their mouse over the smiley face's nose, it turns blue. This is called a hovering effect, and while it has traditionally been used for hyperlinks, it should work on a wide variety of HTML elements. [cite web
url=http://blogs.msdn.com/ie/archive/2006/08/22/712830.aspx
title=Details on our CSS changes for IE7
last=Mielke
first=Markus
work=IEBlog
publisher=Microsoft
date=2006-08-22
accessdate=2008-07-31]

Because Acid2 is not a comprehensive test, it does not guarantee total conformance with any particular standard. A variant of the Acid2 test that does not test for data URI support is also available from the Web Standards Project.

Passing conditions

A passing score is only considered valid if the browser's default settings were used. Actions such as changing font sizes, zoom level, and applying user stylesheets can break the display of the test. This is expected and is not relevant to a browser's compliance.cite web
url=http://www.webstandards.org/2006/07/20/acid2-and-opera-9-clarifications/
title=Acid2 and Opera 9 Clarifications: Yes, Opera 9 Passes the Test
author=Holzschlag, Molly E.
authorlink=Molly Holzschlag
publisher=The Web Standards Project
date=2006-07-20
accessdate=2006-07-22]

The following browser settings and user actions invalidate the test: [cite web
url=http://weblog.timaltman.com/archive/2006/07/19/tims-opera-bits-v11
title=Tim's Opera Bits v1.1
work=Tim's blog
last=Altman
first=Tim
date=2006-07-19
accessdate=2007-11-15]
* Scrolling
* Resizing the browser window
* Zooming in or out
* Disabling images
* Using Opera's "Fit to width" or "Small Screen Rendering" modes
* Applying custom fonts, colors, styles, etc.
* User JavaScript or Greasemonkey scripts

Compliant applications

If rendered correctly, Acid2 will appear as a smiley face below the text "Hello World!" in the user's browser, with the nose turning blue when the mouse cursor hovers over it. At the time of the test's release every browser failed it, but now a number of applications pass the test:

Officially released

* WebKit- and KHTML-based browsers
** Safari, the web browser included in Mac OS X and available for Windows
** OmniWeb, a web browser for Mac OS X
** Shiira, a web browser for Mac OS X
** iCab, a web browser for Mac OS X
** Konqueror, a web browser for KDE
* Prince, an XML-to-PDF converter for Windows, Mac OS X and Linux
* Presto-based browsers
** Opera, an internet suite for Windows, Mac OS X, Linux, and BSD
** The Internet Channel, a version of the Opera browser for the Nintendo Wii game console.
* Gecko-based browsers
** Mozilla Firefox 3, a web browser for Windows, Mac OS X and Linux

In development

* Tkhtml Html Viewer 3, a web browser for Windows and Linux
* Internet Explorer 8
* WebKit- and KHTML-based browsers
** Arora
** Epiphany
** Google Chrome for Windows
* Gecko-based applications
** Camino 2.0, a web browser for Mac OS X
** Fennec, a web browser for mobile devices
** Instantbird 0.1.1, an instant messenger for Windows, Mac OS X and Linux
** K-Meleon, a web browser for Windows
** Mozilla Prism, a web application platform for Windows, Mac OS X and Linux
** Mozilla Thunderbird 3, an email client for Windows, Mac OS X and Linux
** Mozilla Sunbird 1.0, a calendar application for Windows, Mac OS X and Linux
** SeaMonkey 2, an internet suite for Windows, Mac OS X and Linux
** Songbird 0.7, a media player and web browser for Windows, Mac OS X
** Spicebird 0.7, a personal information manager for Windows, Mac OS X and Linux

Non-compliant applications

In July 2005, Chris Wilson, the Internet Explorer Platform Architect, stated that passing Acid2 was not a priority for Internet Explorer 7, describing the test as a "wish list" of features rather than a true test of standards compliance. [cite web
url=http://blogs.msdn.com/ie/archive/2005/07/29/445242.aspx
title=Standards and CSS in IE
last=Wilson
first=Chris
work=IEBlog
publisher=Microsoft
date=2005-07-29
accessdate=2008-03-11] In December 2007, Microsoft announced that all the changes required to pass Acid2 would be made available in Internet Explorer 8, but that the changes would not be turned on by default, meaning that IE8 would not actually pass the test. [cite web
url=http://channel9.msdn.com/posts/Charles/IE-8-On-the-Path-to-Web-Standards-Compliance-ACID-2-Test-Pass-Complete/
title=IE 8: On the Path to Web Standards Compliance - ACID 2 Test Pass Complete
author=Charles
publisher=Microsoft
date=2007-12-19
accessdate=2008-08-30 About 19 minutes and 15 seconds through the video, Alex Mogilevsky, a member of the IE team, points at a picture of the Acid2 test improperly rendered and states "The video in the bottom is a IE7 version of smiley face...What you're looking at is actually IE8. It is what it looks currently in IE8 and it will look exactly like this when we ship IE8 because we are not breaking any compatibility, and this is a compatible mode of IE8. And, uh, most of the web relies on particular behavior including particular "incorrect" behavior, so the incorrect behavior will still be there unless the new content "wants" IE to be in standards-compliant mode, and then they will ask us, and then we will show perfectly standard picture."] [cite web
url=http://people.opera.com/howcome/2007/msft/acid2.html
title=Acid2 in IE8!
author=Lie, Håkon Wium
publisher=Opera Software
date=2007-12-20
accessdate=2008-08-30] Then in March 2008 Microsoft released IE8 beta 1 and turned on the changes by default after all, [cite web
url=http://blogs.msdn.com/ie/archive/2008/03/03/microsoft-s-interoperability-principles-and-ie8.aspx
title=Microsoft's Interoperability Principles and IE8
last=Hachamovitch
first=Dean
work=IEBlog
publisher=Microsoft
date=2008-03-03
accessdate=2008-08-30] but another unresolved standards compliance issue prevented it from passing in some cases.cite web
url=http://blogs.msdn.com/ie/archive/2008/03/05/why-isn-t-ie8-passing-acid2.aspx
title=Why Isn't IE8 Passing Acid2?
publisher=Microsoft
first=Phil
last=Nachreiner
date=2008-03-05
accessdate=2008-03-11] [cite web
url=http://www.w3.org/TR/1999/REC-html401-19991224/struct/objects.html#h-13.3.1
title=Objects, Images, and Applets: Rules for rendering objects
work=HTML 4.01 Specification
publisher=W3C
date=1999-12-24
accessdate=2008-03-20] [cite web
url=http://lists.w3.org/Archives/Public/www-archive/2008Mar/0018.html
title=Re: MSIE 8 beta 1 clarification needed
last=Hickson
first=Ian
publisher=World Wide Web Consortium
date=2008-03-14
accessdate=2008-05-05] Microsoft released IE8 beta 2 in August 2008, which resolved the issue, however in IE8 beta 2 standards mode is not turned on by default for pages loaded in the "Intranet Zone". This zone is active for pages loaded via UNC Paths, named addresses without dots (eg. http://mysite/) and sites that bypass the proxy settings. [cite web
url=http://support.microsoft.com/kb/174360
title=How to use security zones in Internet Explorer
Work=Microsoft Knowledge Base
publisher=Microsoft
date=2007-12-18
accessdate=2008-08-31] As such, IE8 will not pass the Acid2 test if loaded in these cases. [cite web
url=http://blogs.msdn.com/ie/archive/2008/08/27/introducing-compatibility-view.aspx
title=Introducing Compatibility View
last=Dickens
first=Scott
work=IEBlog
publisher=Microsoft
date=2008-08-27
accessdate=2008-08-30]

Even though Opera Mini is based on the same rendering engine as Opera for personal computers, it does not pass the Acid2 test. [cite web
url=http://virtuelvis.com/archives/2007/06/opera-mini-4-beta
title=Opera Mini 4 beta out
last=Bersvendsen
first=Arve
month=June
year=2007
accessdate=2007-12-22] [cite web
url=http://www.operamini.com/demo/
title=Opera Mini Simulator
publisher=Opera Software
accessdate=2007-12-22] This is because Opera Mini intentionally reformats web pages to try and make them more suitable for devices with small screens. [cite web
url=http://www.operamini.com/features/
title=Opera Mini Features
publisher=Opera Software
accessdate=2007-12-21] [cite web
url=http://simonwillison.net/2006/May/11/operamini/#c33322
title=c33322
author=Wilton-Jones, Mark "Tarquin"
publisher=Simon Willison
date=2006-06-10
accessdate=2008-05-10]

As of September 2008, approximately 78% of the Web browser market share does not pass the Acid2 test. [cite web
url=http://marketshare.hitslink.com/report.aspx?qprid=2
title=Browser Version Market Share
publisher=Net Applications
month=August
year=2008
accessdate=2008-08-01]

---

Internet Explorer 6

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Internet Explorer 7
Mozilla Firefox 1.0, Mozilla 1.7.13, and Netscape 7.2

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Mozilla Firefox 1.5 and 2.0
Opera 8.0
Opera 8.54
Konqueror 3.4
Opera Mini 4
iPod touch 2.0
NetSurf 1.2

Timeline of passing applications

The following is a list of releases noting significant releases of applications that passed the test. New applications that have passed Acid2 since their first official release are not included in the timeline.

ee also

* Comparison of layout engines

References

External links

* [http://acid2.acidtests.org/ The Second Acid Test]
* [http://www.webstandards.org/action/acid2/ Acid2 test information]
* [http://acidtests.googletoad.com/ The Acid2 Test Results]
* [http://www.howtocreate.co.uk/acid/ Acid 2 in major browsers]
* [http://www.acidtests.org/ The Web Standards Project's collection of Acid tests]
* [http://www.webstandards.org/press/releases/20050413// April 13, 2005 Web Standards Project press release]
* [http://news.cnet.com/The-Acid2-challenge-to-Microsoft/2010-1032_3-5618723.html CNET article proposing the Acid2 test]
* [http://www.hyperborea.org/journal/archives/2005/11/01/acid2-timeline/ Acid2 timeline]