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 Though
released in 1995 as part of the initial OEM release of Windows 95,
Internet Explorer was not included in the first retail, or shrink-wrap,
release of Windows 95. The last major upgrade to Internet Explorer, 6.0
SV1[1], is included in Windows XP Service Pack 2 and Windows Server 2003
Service Pack 1 only. Version 7 of Internet Explorer is currently under
development; beta versions have been released on a regular basis, most
recently build 5346.5 released April 24, 2006. Versions of Internet
Explorer prior to 6.0 SV1 are also available as a separate download for
versions of Windows up to Windows XP. There is a version for Windows CE
and Mobile called Pocket Internet Explorer.
After the first release for Windows 95, additional versions of Internet
Explorer were developed for other operating systems: Internet Explorer
for Mac and Internet Explorer for UNIX (the latter for use through the X
Window System on Solaris and HP-UX). Only the Windows version remain in
active development.
Internet Explorer versions 6 and below are known as "Microsoft Internet
Explorer". This will change in version 7, with the name being "Windows
Internet Explorer". History
Internet Explorer is derived primarily from Spyglass Mosaic, an early
commercial web browser. In 1995, Spyglass Mosaic was licensed by
Microsoft in an arrangement under which Spyglass would receive a
quarterly fee plus a percentage of Microsoft's revenues for the
software. Although bearing a name similar to NCSA Mosaic, which was the
first widely used browser, Spyglass Mosaic was relatively unknown in its
day and used the NCSA Mosaic source code only sparingly [2].
Internet Explorer was not widely used until the release of version 3,
when Internet Explorer was integrated into Windows Explorer and other
core parts of Windows. This was also the first version developed without
Spyglass sources. The integration with Windows, however, was subject to
numerous criticisms (see United States v. Microsoft).
Internet Explorer 3 was the first major browser with CSS support.
Released on August 13, 1996, it introduced support for ActiveX controls,
Java applets, inline multimedia, and the PICS system for content
metadata. These improvements were significant, compared to its main
competitor at the time, Netscape Navigator. Version 3 also came bundled
with Internet Mail and News, NetMeeting, and an early version of the
Windows Address Book, and was itself included with Windows 95 OSR 2.
Version 3 proved to be the first popular version of Internet Explorer,
which brought with it increased scrutiny. In the months following its
release, a number of security and privacy vulnerabilities were being
found by researchers and hackers.
Version 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 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. 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. 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.
Version 5, launched on March 18, 1999, and subsequently included with
Windows 98 Second Edition and Windows 2000, and bundled with Office
2000, was another significant release that supported bi-directional
text, ruby characters, XML, XSL and the ability to save web pages in
MHTML format. Version 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.
Version 6 was released on August 27, 2001, a few weeks before Windows
XP. This version included DHTML enhancements, content restricted inline
frames, and better 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 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.
On February 15, 2005, Microsoft Chairman Bill Gates announced that the
new version of its browser would be released at the RSA Conference 2005
in San Francisco [3]. The decision to update the browser occurred in the
wake of a decline in the use of Internet Explorer for the first time.
Microsoft also stated that Internet Explorer 7 will only be available
for Windows XP SP2 and later, including Windows Server 2003 SP1 and
Windows Vista. The first beta version of the browser was released on
July 27, 2005 for technical testing, and a first public preview version
of Internet Explorer 7 (Beta 2 preview: Pre-Beta 2 version) was released
on January 31, 2006. Version 7 is intended to defend users from phishing
as well as deceptive or malicious software, and also features full user
control of ActiveX, and better security framework. It includes important
bug fixes, enhancements to support the web standards, improvements in
HTML 4.01/CSS 2, Tabbed Browsing, Tab preview and management, and web
feeds reader. Features
The pop-up blocker included in Internet Explorer 6 SP2Internet Explorer
has been designed to view the broadest range of web pages and to provide
certain features within the operating system, including Windows Update.
During the heydays of the historic browser wars, Internet Explorer
superseded Netscape by supporting many of the progressive features of
the time.
Component architecture
The Component Object Model (COM) technology is used extensively in
Internet Explorer. It allows third parties to add functionality via
Browser Helper Objects (BHO); and allows websites to offer rich content
via ActiveX. As these objects can have the same privileges as the
browser itself (in certain situations), there is a concern over
security. This issue was addressed in Internet Explorer 6.0 SV1, which
provides an Add-on Manager for controlling ActiveX controls and Browser
Helper Objects. Internet Explorer 7 provides a "No Add-Ons" version
(Under Programs/Accessories/System Tools) to address this issue, as
well.
Usability and accessibility
Since it is tightly integrated with the operating system, Internet
Explorer makes use of the accessibility framework provided in Windows.
Internet Explorer is also a user interface for FTP, with operations
similar to that of Windows Explorer.
The ability to block popup windows was introduced with Internet Explorer
6.0, Service Pack 2.
Tabbed browsing can be added to Internet Explorer 6 by installing
Microsoft's MSN Search Toolbar, and is natively supported as of Internet
Explorer 7.
Security framework
Internet Explorer uses a zone-based security framework, which means
that sites are grouped based upon certain conditions. It allows the
restriction of broad areas of functionality, and also allows specific
functions to be restricted.
Patches and updates to the browser are released periodically and made
available through the Windows Update, as well as through Automatic
Updates. Although security patches continue to be released for a range
of platforms, most recent feature additions and security improvements
are released for Windows XP only.
Internet Explorer 6 Service Pack 2 provides Download Monitoring and
Install Monitoring that user can choose to download, or not to download
and, choose to install, or not to install Applications, Executables and
Installations. This helps to prevent installation of malware. Executable
files downloaded using Internet Explorer are marked by the operating
system as being potentially unsafe, and will prompt the user to confirm
they want to run the executable every time, until the user confirms the
file is "safe".
Group Policy
Internet Explorer is fully configurable using Group Policy.
Administrators of Windows Server domains can apply and enforce a variety
of settings that affect the user interface (such as disabling menu items
and individual configuration options), as well as underlying security
features such as downloading of files, zone configuration, per-site
settings, ActiveX control behavior, and others. Policy settings can be
configured on a per-user and per-machine basis.
Standards support
Internet Explorer, using the Trident layout engine, almost fully
supports HTML 4.01, CSS Level 1, XML 1.0 and DOM Level 1, with minor
implementation gaps. It partially supports CSS Level 2 and DOM Level 2,
with some implementation gaps and conformance issues. It supports XHTML
1.0 to the extent that HTML 4.01 compatibility guidelines are followed.
Internet Explorer uses DOCTYPE sniffing to choose between "quirks mode"
(renders similarly to older versions of MSIE) and standards mode
(renders closer to W3C's specifications) for HTML and CSS rendering. It
fully supports XSLT 1.0 or the December 1998 Working Draft of XSL,
depending on the version of MSXML (a dynamic link library) available. It
also provides its own dialect of ECMAScript called JScript.
Proprietary extensions
Internet Explorer has introduced an array of proprietary extensions
to many of the standards, including HTML, CSS and the DOM. This has
resulted in a number of web pages that can only be viewed properly using
Internet Explorer. Many view this as an example of what is called
"embrace, extend and extinguish", a way to drive competitors out of
business by forcing them to use proprietary technology that a company
controls, resulting in vendor lock-in. Netscape Navigator up to version
4.7 was also responsible for massive proprietary extension of the core
web standards, but was not criticized for it as much.
Criticisms Much criticism towards Internet Explorer is
related to concerns about security: Much of the spam, spyware, adware,
and computer viruses across the Internet is made possible by exploitable
bugs and flaws in the security architecture of Internet Explorer. While
Internet Explorer is not alone in having exploitable vulnerabilities,
its ubiquity has resulted in many more affected computers when
vulnerabilities are found.
Microsoft has also not responded as quickly as competitors in fixing
security holes and making patches available. Not only are there more
discovered holes in Explorer, but holes remain unpatched for a longer
time. Several companies maintain databases of known security
vulnerabilities that exist in Internet Explorer, for which no fixes have
been published by Microsoft. As of May 28, 2006, Secunia reports 101
vulnerabilities in Internet Explorer, 21 of which are unpatched [13]. In
contrast, Mozilla Firefox, the main competitor to Internet Explorer, is
reported to have only 31 security vulnerabilities, of which 4 remain
unpatched [14]. Opera, another competitor to Internet Explorer, has 13
vulnerabilities and none of them remain unpatched. [15]. Lower numbers
are better.
Other criticisms, mostly coming from technically proficient users and
developers of websites and browser-based software applications, concern
Internet Explorer's support of open standards, because the browser often
uses proprietary extensions to achieve similar functionality. Internet
Explorer supports, to some degree, a number of standardized
technologies, but has implementation gaps and conformance failures—some
minor, some not—that have led to criticism from an increasing number of
developers. The increase is attributable, in large part, to the fact
that competing browsers that offer relatively thorough,
standards-compliant implementations are becoming more widely used.
Internet Explorer's ubiquity, in spite of its perceived inferiority in
this area, frustrates developers who want to write standards-compliant,
cross-browser code. It can also prevent widespread adoption of new
technologies. Web developers must work with the least advanced
technology across all browsers they wish to support, and Internet
Explorer is often criticized for often having the least advanced
support. For a long-standing concrete example, see Internet Explorer's
poor PNG transparency support.
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