Internet Explorer 6

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Internet Explorer 6
File:Internet Explorer logo old.svg
File:IE 6 SP3 XP screenshot.PNG
Internet Explorer 6 in Windows XP SP3
Developer(s) Microsoft
Initial release August 27, 2001
Stable release 6.0 SV3 ('6 SP3')[1] / May 5, 2008
Operating system Microsoft Windows (98 to WS2003)
Development status Extended support only
Superseded by 7.0
License MS-EULA
Website Internet Explorer 6
1 · 2 · 3 · 4 · 5 · 6 · 7 · 8 · 9
Microsoft Internet Explorer 6
A component of Microsoft Windows
Included with Windows XP and Windows Server 2003
Replaces Microsoft Internet Explorer 5
Replaced by Windows Internet Explorer 7
Related components
Internet Explorer

Internet Explorer 6 (commonly abbreviated as IE6) is the sixth major revision of Internet Explorer, a web browser developed by Microsoft for Windows operating systems. It was released on August 27, 2001, shortly after the completion of Windows XP.

It is the default browser shipped with Windows XP and Windows Server 2003, and was also made available for Windows NT 4.0, Windows 98, Windows ME, and Windows 2000. IE6 SP1 is the last version of Internet Explorer available for Windows 98, Windows ME, and Windows 2000. Although IE6 has now been superseded by newer versions of Internet Explorer, Microsoft still supports it in Windows 2000 SP4 and Windows XP SP3.

This version of Internet Explorer is widely derided for its security issues and lack of support for modern web standards, making frequent appearances in "worst tech products of all time" lists, with some publications labeling it as the "least secure software on the planet."[2] Campaigns have been established in order to encourage users to upgrade to newer versions of Internet Explorer or switch to different browsers, and some websites have dropped support for IE6 entirely.[3][4]



When Internet Explorer 6 was released, it included a number of enhancements over its predecessor, Internet Explorer 5.5. IE6 improved support for Cascading Style Sheets, adding support for a number of properties which previously had not been implemented and fixing bugs such as the Internet Explorer box model bug.[5] In Windows XP, IE6 introduced a redesigned interface based on the operating system's default theme, Luna.

In addition, IE6 added DHTML enhancements, content restricted inline frames, and partial support of DOM level 1 and SMIL 2.0.[6] The MSXML engine was also updated to version 3.0. Other new features included a new version of the Internet Explorer Administration Kit (IEAK), Media bar, Windows Messenger integration, fault collection, automatic image resizing, and P3P. Meanwhile, IE6 dropped support for XBM image files, and in 2002, the Gopher protocol was disabled.[7]

IE6 was the most widely used web browser during its tenure, surpassing Internet Explorer 5.x. At its peak in 2002 and 2003, IE6 attained a total market share of nearly 90%, with all versions of IE combined reaching 95%. There was little change in IE's market share for several years, until Mozilla Firefox was released and gradually began to gain popularity. Microsoft subsequently resumed development of Internet Explorer and released Internet Explorer 7, further reducing the number of IE6 users.

In a May 7, 2003 Microsoft online chat, Brian Countryman, Internet Explorer Program Manager, declared that Internet Explorer would cease to be distributed separately from Windows (IE 6 would be the last standalone version);[8] it would, however, be continued as a part of the evolution of Windows, with updates coming only bundled in Windows upgrades. Thus, Internet Explorer and Windows itself would be kept more in sync. However, after one release in this fashion (IE6 SP2 in Windows XP SP2, in August 2004), Microsoft changed its plan and released Internet Explorer 7 for Windows XP SP2 and Windows Server 2003 SP1 in late 2006. Microsoft Internet Explorer 6 was the last version of Internet Explorer not to have "Windows" in the title, with later versions shifting to "Windows Internet Explorer", as a reaction to the allegations of anti-competitive tying of Internet Explorer and Windows raised in United States v. Microsoft and the European Union Microsoft competition case.

Security issues

As of January 10, 2009, security advisory site Secunia reports 142 vulnerabilities in Internet Explorer 6, 22 of which are unpatched, some of which are rated moderately critical in severity[9].

Although security patches continue to be released for a range of platforms, most recent feature additions and security improvements were released for Windows XP only.

As of June 23, 2006, Secunia counted 20 unpatched security flaws for Internet Explorer 6, many more and older than for any other browser, even in each individual criticality-level, although some of these flaws only affect Internet Explorer when running on certain versions of Windows or when running in conjunction with certain other applications.[10]

On June 23, 2004, an attacker used two previously undiscovered security holes in Internet Explorer to insert spam-sending software on an unknown number of end-user computers.[11] This malware became known as Download.ject and it caused users to infect their computers with a back door and key logger merely by viewing a web page. Infected sites included several financial sites.

Probably the biggest generic security failing of Internet Explorer (and other web browsers too) is the fact that it runs with the same level of access as the logged in user, rather than adopting the principle of least user access. Consequently any malware executing in the Internet Explorer process via a security vulnerability (e.g. Download.ject in the example above) has the same level of access as the user, something that has particular relevance when that user is an Administrator. Tools such as DropMyRights are able to address this issue by restricting the security token of the Internet Explorer process to that of a limited user. However this added level of security is not installed or available by default, and does not offer a simple way to elevate privileges ad-hoc when required (for example to access Microsoft Update).

Art Manion, a representative of the United States Computer Emergency Readiness Team (US-CERT) noted in a vulnerability report that the design of Internet Explorer 6 Service Pack 1 made it difficult to secure. He stated that:

There are a number of significant vulnerabilities in technologies relating to the IE domain/zone security model, local file system (Local Machine Zone) trust, the Dynamic HTML (DHTML) document object model (in particular, proprietary DHTML features), the HTML Help system, MIME type determination, the graphical user interface (GUI), and ActiveX. … IE is integrated into Windows to such an extent that vulnerabilities in IE frequently provide an attacker significant access to the operating system.[12]

Manion later clarified that most of these concerns were addressed in 2004 with the release of Windows XP Service Pack 2, and other browsers have now begun to suffer the same vulnerabilities he identified in the above CERT report.[13]

Many security analysts[who?] attribute Internet Explorer's frequency of exploitation in part to its ubiquity, since its market dominance makes it the most obvious target. However, some critics[who?] argue that this is not the full story, noting that Apache HTTP Server, for example, had a much larger market share than Microsoft IIS, yet Apache had traditionally had fewer (and generally less serious) security vulnerabilities than IIS, at the time.[14]

As a result of its many problems, some security experts, including Bruce Schneier, recommend that users stop using Internet Explorer for normal browsing, and switch to a different browser instead.[15] Several notable technology columnists have suggested the same, including the Wall Street Journal's Walt Mossberg,[16] and eWeek's Steven Vaughan-Nichols.[17] On July 6, 2004, US-CERT released an exploit report in which the last of seven workarounds was to use a different browser, especially when visiting untrusted sites.[18]

Market share

It was the most widely used web browser during its tenure (surpassing Internet Explorer 5.x), attaining a peak in usage share during 2002 and 2003 in the high 80s, and together with other versions up to 95%. It only slowly declined up to 2007, when it lost about half its market share to Windows Internet Explorer 7 and Mozilla Firefox between late 2006 to 2008.

IE6 remained more popular than its successor in business use for more than a year after IE7 came out.[19] A DailyTech article noted, "A Survey found 55.2% of companies still use IE 6 as of December 2007", while "IE 7 only has a 23.4 percent adoption rate".[19]

Net Applications estimated IE6 market share at almost 39% for September, 2008[20]. According to the same source, IE7 users migrate faster to IE8 than users of its predecessor IE6 does. This led to IE6 once again becoming the most widely used browser version. During the summer and fall of 2009, 8 years after its introduction, IE6 still held the top spot in terms of browser marketshare [21].

As of January 2010, estimates of IE6's global market share ranged from 11-20%.[22][23][24]

Nonetheless, IE6 continues to maintain a plurality or even majority presence in the browser market of certain countries, notably China[25] and South Korea[26].


A common criticism of Internet Explorer is of the speed at which fixes are released after discovery of the security problems.

Microsoft attributes the perceived delays to rigorous testing. A posting to the Internet Explorer team blog on August 17, 2004 explained that there are, at minimum, 234 distinct releases of Internet Explorer that Microsoft supports (covering more than two dozen languages, and several different revisions of the operating system and browser level for each language), and that every combination is tested before a patch is released.[27]

File:Unicode rendering IE.PNG
Internet Explorer also has troubles rendering Unicode characters.

In May 2006, PC World rated Internet Explorer 6 the eighth worst tech product of all time.[2] A certain degree of complacency has been alleged against Microsoft over IE6. With near 90% of the browser market the motive for innovation was not strongly present, resulting in the 5 year time between the IE6's introduction and its replacement with IE7. This fact is one contributing factor for the rapid rise of the open source alternative Mozilla Firefox.

Unlike most other browsers currently in use, IE6 does not fully nor properly support CSS version 2, which makes it difficult for web developers to ensure compatibility with the browser without degrading the experience for users of more modern browsers. Developers often have to resort to strategies such as CSS hacks, conditional comments, or other forms of browser sniffing to make their websites work in IE6.

Additionally, IE6 lacks support for alpha transparency in PNG images, instead removing all transparency and displaying the image with a gray background unless the proprietary AlphaImageLoader filter is used.[28]

IE6 has also been criticized due to its instability. For example, all one must do to cause IE6 to crash is insert this code into a web page:


There are several campaigns aiming to rid Internet Explorer 6, which is still used by 20% of Internet surfers,[29] from the browser market:

  • is one such example
  • In February 2009, some Norwegian sites began hosting campaigns with the same aim.[30]
  • In March 2009, a Danish anti-IE6 campaign was launched.[31]
  • In January 2010, the German Government, and subsequently the French Government each advised their citizens to move away from IE6[32]
  • Also in January 2010, Google announced it would no longer support IE6[33]
  • In February 2010, British citizens began to petition their Government to stop using IE6[34]

With the increasing lack of compatibility with modern web standards, much larger web-sites are starting to remove support for IE6, including YouTube[3] and their parent company Google[4], however with large company IT support teams forcing staff to use IE6 it is unlikely Microsoft will completely remove support for the aging browser any time in the near future.[35] Microsoft have themselves, despite admitting to some of its many flaws, stated that they will support IE6 until Windows XP SP3 support is removed, meaning IE6 will be officially around until 2014, 13 years after its release[36].

Security framework

Internet Explorer uses a zone-based security framework, which means that sites are grouped based upon certain conditions. IE allows the restriction of broad areas of functionality, and also allows specific functions to be restricted. The administration of Internet Explorer is accomplished through the Internet Properties control panel. This utility also administers the Internet Explorer framework as it is implemented by other applications.

Patches and updates to the browser are released periodically and made available through Windows Update web site. Windows XP Service Pack 2 adds several important security features to Internet Explorer, including a popup blocker and additional security for ActiveX controls. ActiveX support remains in Internet Explorer although access to the "Local Machine Zone" is denied by default since Service Pack 2. However, once an ActiveX control runs and is authorized by the user, it can gain all the privileges of the user, instead of being granted limited privileges as Java or JavaScript do. This was later solved in the Windows Vista version of IE 7, which supported running the browser in a low-permission mode, making malware unable to run unless expressly granted permission by the user.

Quirks Mode

Internet Explorer 6 dropped Compatibility Mode, which allowed Internet Explorer 4[37] to be run side by side with 5.x.[38][39] Instead, IE6 introduced quirks mode, which causes it to emulate many behaviors of IE 5.5.[40] Rather than being activated by the user, quirks mode is automatically and silently activated when viewing web pages that contain an old or invalid DOCTYPE (or none at all). This feature was later added to all other major browsers to maximize compatibility with old or poorly-coded web pages.[41]

Supported platforms

Internet Explorer 6.0 supports Windows NT 4.0 (Service Pack 6a only), Windows 98, Windows Me, Windows 2000, Windows XP and Windows Server 2003. The Service Pack 1 update supports all of these versions, but Security Version 1[1] is only available as part Windows XP Service Pack 2 and Windows Server 2003 Service Pack 1 and later service packs for those versions. Versions after Windows XP include Internet Explorer 7 and higher only.

Release history

Major version Minor version Release date Significant changes Shipped with
Version 6 6.0 Beta 1 March 2001 More CSS changes and bug fixes to be more W3C-compliant.
6.0 August 27, 2001 Final release. Windows XP
6.0 SP1 September 9, 2002 Vulnerability patch. Last version supported on Windows NT 4.0, 98, 2000 or Me. Windows XP SP1 and Windows Server 2003
6.0 SP2 August 25, 2004 Vulnerability patch. Popup/ActiveX blocker. Add-on manager. Windows XP SP2 and Windows Server 2003 SP1
6.0 SP3 April 21, 2008 Latest updates included with XP SP3 Windows XP SP3

System requirements

IE6 requires at least[42] (with added requirements for XP by IE6 SP1[43]):

See also


  1. 1.0 1.1 SV1 stands for "Security Version 1", referring to the set of security enhancements made for that release.Template:Ref label This version of Internet Explorer is more popularly known as IE6 SP2, given that it is included with Windows XP Service Pack 2, but this can lead to confusion when discussing Windows Server 2003, which includes the same functionality in the SP1 update to that operating system. —
    ^ "XPSP2 and its slightly updated user agent string". The Windows Internet Explorer Weblog. Microsoft via MSDN. 2004-09-02. Retrieved 2008-10-05. 
  2. 2.0 2.1 PCWorld (2005-05-26). "The 25 Worst Tech Products of All Time".,aid,125772,pg,3,00.asp. Retrieved 2006-07-18. 
  3. 3.0 3.1 TechRadar (2009-07-14). "Official: YouTube to stop IE6 support". Retrieved 2009-07-26. 
  4. 4.0 4.1 CNET (2010-01-30). "Google phasing out support for IE6". Retrieved 2010-01-30. 
  5. "MSDN". CSS Enhancements in Internet Explorer 6. Microsoft. September 2006. 
  6. "SMIL Standards and Microsoft Internet Explorer 6, 7, and 8". Retrieved 2007-05-27. 
  7. "Using a web browser to access gopher space". Retrieved 2007-05-11. 
  8. Microsoft to abandon standalone IE, January 23, 2006
  9. Microsoft Internet Explorer 6.x, Secunia
  10. "Vulnerability Report – Microsoft Internet Explorer 6.x". Secunia. Retrieved 2006-06-23. 
  11. "Researchers warn of infectious Web sites". June 25, 2004. Retrieved 2006-04-07. 
  12. "Vulnerability Note VU#713878". US-CERT. June 9, 2004. Retrieved 2006-04-07. 
  13. "Perspective: A safe browser? No longer in the lexicon". CNet. July 7, 2005. Retrieved 2006-04-07. 
  14. Wheeler, David (November 14, 2005). "Why Open Source Software / Free Software (OSS/FS, FLOSS, or FOSS)? Look at the Numbers!". 
  15. "Safe Personal Computing". December 12, 2004. Retrieved 2006-04-07. 
  16. Mossberg, Walt (September 16, 2004). "How to Protect Yourself From Vandals, Viruses If You Use Windows". Personal Technology. Wall Street Journal.,,SB109528585699018983-email,00.html. Retrieved 2006-04-07. 
  17. Vaughan-Nichols, Steven (June 28, 2004). "Internet Explorer Is Too Dangerous to Keep Using". Linux & Open Source – Opinions. eWeek.,1759,1617931,00.asp. Retrieved 2006-04-07. 
  18. "Vulnerability Note VU#713878". US-CERT. June 9, 2004. Retrieved 2006-04-07. 
  19. 19.0 19.1 Mick, Jason (2008-04-03). "Firefox Makes Big Gains In Business at IE's Expense". DailyTech. Retrieved 2008-10-05. 
  20. "Top Browser Share Trend". Net Applications. September 2008. Retrieved 2008-10-05.  The date range spans October, 2006—September, 2008.
  22. "Global Web Stats". W3Counter. January 2010. Retrieved 2010-02-03. 
  23. "StatCounter Global Stats". StatCounter. January 2010. Retrieved 2010-02-03. 
  24. "Browser Version Market Share". Net Applications. January 2010. Retrieved 2010-02-03. 
  27. "The Basics of the IE Testing Matrix". Internet Explorer team blog. Microsoft. August 17, 2004. Retrieved 2006-04-07. 
  28. "Microsoft Help and Support". PNG Files Do Not Show Transparency in Internet Explorer. Microsoft. July 19, 2007. 
  29. "Browser Version Market Share". Net Applications. 2010-02-01. Retrieved 2010-02-01. 
  35. The Register (2009-07-08). "Orange UK exiles Firefox from call centres". Retrieved 2009-07-26. 
  36. BBC News (2009-08-13). "Microsoft backs long life for IE6". Retrieved 2009-08-21. 
  37. "How to install and use Compatibility mode in Internet Explorer 5 or 5.5 (KB197311)". Microsoft Help and Support. 2007-01-23. Retrieved 2008-10-05. 
  38. "Unable to Use Internet Explorer 4.0 Compatibility Mode (KB237787)". Microsoft Help and Support. 2007-01-24. Retrieved 2008-10-05. 
  39. Hardmeier, Sandi (2005-08-25). "The History of Internet Explorer". Internet Explorer Community. Retrieved 2008-10-05. 
  40. Chao, Ingo; Holly Bergevin, Bruno Fassino, John Gallant, Georg Sørtun, Philippe Wittenbergh (2005-08-15). "Quirks mode in IE 6 and IE 7". Retrieved 2008-10-05.  Last updated on June 3, 2006.
  41. "Quirks Mode and Strict Mode". QuirksMode. 
  42. "Internet Explorer 6 System Requirements". Microsoft. 2001-08-27. Retrieved 2009-10-12. 
  43. "Internet Explorer 6 SP1 System Requirements". Microsoft. 2002-09-09. Retrieved 2009-11-14. 

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