Internet Explorer 4, released in September 1997, deepened the level of integration between the web browser and the underlying operating system. Installing version 4 on a Windows 95 or Windows NT 4 machine and choosing "Windows Desktop Update" would result in the traditional Windows Explorer also being replaced by a version more akin to a web-browser interface, as well as the Windows desktop itself being web-enabled via Active Desktop. The integration with Windows, however, was subject to numerous packaging criticisms (see United States v. Microsoft). This option was no longer available with the installers for later versions of Internet Explorer but was not removed from the system if already installed. Internet Explorer 4 introduced support for Group Policy, allowing companies to configure and lock down many aspects of the browser's configuration as well as support for offline browsing. Internet Mail and News was replaced with Outlook Express, and Microsoft Chat and an improved NetMeeting were also included. This version also was included with Windows 98. New features were added that allow you to save and retrieve posts in comment forms which are still not being used today. Internet Explorer 4.5 offered new features such as easier 128-bit encryption. It also offered a dramatic stability improvement over prior versions, particularly the 68k version which was especially prone to freezing.
Internet Explorer 5 was launched on March 18, 1999, later included with Windows 98 Second Edition and came with Office 2000. The creation of Internet Explorer 5 was another significant release that supported bi-directional text, ruby characters, XML, XSLT, and the ability to save web pages in MHTML format. IE5 was bundled with Outlook Express 5. Also, with the release of Internet Explorer 5.0, Microsoft released the first version of XMLHttpRequest, giving birth to Ajax (even though the term "Ajax" was not coined until years later). It was the last with a 16-bit version. Internet Explorer 5.01, a bug fix version, was released in December 1999. Windows 2000 includes this version. Internet Explorer 5.5 followed in July 2000, improving its print preview capabilities, CSS and HTML standards support, and developer APIs; this version was bundled with Windows Me. However, version 5 was the last version for Mac and UNIX. Version 5.5 was the last to have "Compatibility Mode", which allowed Internet Explorer 4 to be run side by side with the 5.x. The IE team consisted of over 1,000 people by 1999, with funding on the order of 100 million USD per year.
Internet Explorer 6 was released on August 27, 2001, a few months before Windows XP. This version included DHTML enhancements, content restricted inline frames, and partial support of CSS level 1, DOM level 1, and SMIL 2.0. 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, P3P, and a new look-and-feel that was in line with the "Luna" visual style of Windows XP, when used in Windows XP. Internet Explorer 6.0 SP1 offered several security enhancements and coincided with the Windows XP SP1 patch release. In 2002, the Gopher protocol was disabled and support for it was dropped in Internet Explorer 7. Internet Explorer 6.0 SV1 came out August 6, 2004 for Windows XP SP2 and offered various security enhancements and new color buttons on the user interface. IE6 updated the original 'blue e' logo to a lighter blue and more 3D look. Microsoft now considers IE6 to be an obsolete product and recommends that users upgrade to IE8. Many corporate IT users have not upgraded despite this.
Internet Explorer 7 was released on October 18, 2006. It includes bug fixes, enhancements to its support for web standards, tabbed browsing with tab preview and management, a multiple-engine search box, a web feeds reader, Internationalized Domain Name support (IDN), Extended Validation Certificate support, and anti-phishing filter. With IE7, Internet Explorer has been decoupled from the Windows Shell - unlike previous versions, the Internet Explorer ActiveX control is not hosted in the Windows Explorer process, but rather runs in a separate Internet Explorer process. It is included with Windows Vista and Windows Server 2008, and is available for Windows XP Service Pack 2 and later, and Windows Server 2003 Service Pack 1 and later. The original release of Internet Explorer 7 required the computer to pass a Windows Genuine Advantage validation check prior to installing, but on October 5, 2007, Microsoft removed this requirement. As some statistics show, by mid-2008, Internet Explorer 7 market share exceeded that of Internet Explorer 6 in a number of regions.
Internet Explorer 8 was released on March 19, 2009. It had been in development since August 2007 at the latest. On March 5, 2008, the first public beta (Beta 1) was released to the general public. On August 27, 2008, the second public beta (Beta 2) was released. It is supported in Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista, Windows 7, and Windows Server 2008 on both 32-bit as well as 64-bit architectures. Internet Explorer 8 (IE8) RC1 was released on January 26, 2009. Internet Explorer 8 "Final" was released on March 19, 2009. Security, ease of use, and improvements in RSS, CSS, and Ajax support are Microsoft's priorities for IE8. It includes much stricter compliance with web standards, including a planned full Cascading Style Sheets 2.1 compliance for the release version. All these changes allow Internet Explorer 8 to pass the Acid2 test. However, to prevent compatibility issues, IE8 also includes the IE7 rendering behavior. Sites that expect IE7 quirks can disable IE8's breaking changes by including a meta element in the HEAD section of the HTML document. IE8 also includes numerous improvements to JavaScript support as well as performance improvements, although it still does not pass the Acid3 test, with version 8.0 scoring 20/100. It includes support for "Accelerators" - which allow supported web applications to be invoked without explicitly navigating to them - and "WebSlices" - which allows portions of page to be subscribed to and monitored from a redesigned "Favorites Bar". Other features include "InPrivate" privacy features and SmartScreen phishing filter.
Internet Explorer 9 was released on March 14, 2011. It will have complete or nearly complete support for all CSS 3 selectors, border-radius CSS 3 property, faster JavaScript, embedded ICC v2 or v4 color profiles, and hardware accelerated rendering using Direct2D and DirectWrite. Microsoft has confirmed that Web Open Font Format (WOFF) will also be supported. WOFF is "a strong favorite" for standardization by the Web Fonts Working Group of W3C.
IE9 is supposed to fix many issues with Internet Explorer, including support of the CSS3 standard border-radius property, which means that people using IE9 will be able to see rounded corners, the same way people using Firefox can.
Microsoft has continued to downplay the importance of passing the Acid3 test,
but speculation that IE9 would support the SVG W3C recommendation was ignited when Microsoft announced they had joined the SVG Working Group.