Microsoft today released the first beta of Internet Explorer 9. Coming after four developer-oriented preview releases, the new browser brings a streamlined user interface and a core that is more standards-compliant—and orders of magnitude faster—than any previous version of Internet Explorer.

With Internet Explorer 9, Microsoft is imploring us to "unlock the beauty of the web," and indeed, IE9 is a fast and attractive Web browser. But it has its work cut out if it's going to return the Redmond browser to the unassailable leading position it once had.

A long way down

Microsoft's browser has come a long way since its heyday. Once upon a time, Internet Explorer ruled the world. It was released into a market that was completely dominated by Netscape Navigator, but through a combination of aggressive pricing, regular releases, stability, performance, and standards compliance—not to mention being bundled with Windows—Internet Explorer first matched, and then eclipsed Netscape's market share. With the 2001 release of Internet Explorer 6, Redmond's browser peaked with a market share of over 90%.

But when you reach the top, the only place to go is down, and Internet Explorer has certainly done that. After winning the browser wars and vanquishing Netscape, Microsoft essentially gave up on making a Web browser. The team that worked on IE was disbanded; the focus was on servicing the browser—patching security flaws—rather than actually developing it, to make it a better browser. Microsoft even announced that future versions of the browswer would be completely tied to operating system releases; the company would no longer ship browsers that worked on multiple Windows versions. It made a kind of sense, in a way: the major commercial competitor, Netscape, was reeling, and Microsoft thought it had won control of the Web, so why bother spending money developing a browser?

But the market, of course, did not stand still.

Beyond IE: security and standards

The trouble started when issues became a mainstream concern, and ordinary Web users began to care that their browser and operating system were insecure. Internet Explorer 6 may not have been any worse in this regard than its contemporaries, but as new browsers emerged, its track record became an increasing liability. True to the 2003 decision to cease offering standalone browser versions, Internet Explorer 6 received a modest update in Windows XP Service Pack 2, but those updates were not offered to users of other operating systems. Service Pack 2 brought a number of security improvements to the browser, in an effort to stem the flow of security flaws, but even with this work, Internet Explorer 6 looked increasingly bad—which frustrated Microsoft employees as well as everyone else.

Web developers, too, started to look beyond Internet Explorer. Though it may seem surprising today, the Microsoft browser was once the vanguard of Web standards. Its support for important standards like HTML and CSS, the twin technologies used to write and design webpages, was better than any of its mainstream competitors. Its core technology—the Trident rendering engine, which takes HTML and CSS and presents them on-screen—was fast and efficient. But it wasn't perfect. It didn't do everything the standards said it should; it had bugs and omissions that caused more work for developers.

Microsoft also failed to include support for new and emerging standards. CSS and HTML were both updated, and new specifications, like SVG vector graphics, were created. Internet Explorer didn't keep up; Redmond's interests were only in fixing security flaws.

The competition

Underlying this increased demand for security and standards was a new kind of competition. In beating Netscape, Microsoft may have brought about the death of mainstream, commercial browsers, but in so doing, it also planted the seeds for a new breed of open source browsers. As a last-ditch effort to remain relevant, Netscape open-sourced its browser. This wasn't enough to save Netscape, but that open-source effort evolved into the browser now known as Firefox. Open source was also instrumental in the creation of both Apple's Safari and Google's Chrome. They both use the WebKit rendering engine, an open-source derivative of the also open-source KHTML engine.

Bit by bit, these competing efforts—Firefox, Safari, and Chrome—have eaten away at Internet Explorer's market share. Internet Explorer 6's stagnation, especially in the face of progress from Firefox, left it looking tired and old. At first only nerds and techies, lured by the promise of better conformance and security, defected from Internet Explorer. But Firefox's momentum grew ever stronger. It gave its users tabbed browsing and pop-up blocking; it had regular updates; it performed well; it had a rich variety of extensions and add-ons. Firefox became the browser that geeks would recommend to their non-geek friends. It has matured into a solid, reliable, fully featured Web browser commanding some 23% of the market. Taken together, Firefox, Safari, Chrome, and all the other non-Microsoft browsers command about 40% of the market. Internet Explorer is still the dominant force, but its market share today is only 60%—and falling.

Getting the band back together

Eventually, Microsoft saw the error of its ways. The Internet Explorer team was rebuilt, and Internet Explorer was reinstated as a standalone product. In 2006, Internet Explorer 7 shipped for Windows XP and Windows Vista. This gave Internet Explorer users tabbed browsing, phishing protection, and various small standards conformance improvements.

Though the user interface was new, Internet Explorer 7 was not, in truth, particularly different from its predecessor; its core engine shared many of the same foibles. However, it was just different enough that applications written specifically for Internet Explorer 6 would sometimes break. Coupled with Windows Vista's lacklustre adoption, especially in corporate environments, the result was that Internet Explorer 6 continued to see wide usage.

Version 8 of the browser shipped in 2009. Where Internet Explorer 7 could arguably be seen as a stopgap—the addition of tabbed browsing was enough to make the browser seem broadly comparable to its competition, but the engine changes were slight—Internet Explorer 8 was a far more substantial upgrade; it was far more standards-compliant than its predecessors, and it had a new architecture that made it much more resistant to crashes.

Internet Explorer 8 indicated that Microsoft was taking Web standards seriously. In addition to supporting CSS 2.1 and, finally, passing the Acid2 test correctly, Microsoft contributed thousands of test cases to the CSS 2.1 specification. These tests enabled browser developers to quickly and easily assess their browsers' implementations of specific features of the specification. Building tests isn't sexy or glamorous, but it is a necessary part of building robust, reliable software. Without such tests, it becomes very hard to assess whether or not a browser really does properly implement the specifications it is supposed to implement.

Though far better than its predecessors, Internet Explorer 8 has not been able to stop Microsoft's browser market share slide. Internet Explorer 8 itself is the most widely-used individual browser on the Internet, and has been growing strongly. But Internet Explorer as a whole is still tending to lose market share. Most frustratingly for Web developers, Internet Explorer 6 still retains about 16% of the market—more than version 7—likely due to corporations who cannot or will not switch away from Windows XP.

It's perhaps not hard to understand why. For all the progress Internet Explorer 8 made in terms of standards compliance or performance, it still lags behind its mainstream competition in each of these areas, and it doesn't support most of the new HTML5 features that are currently being specified by W3C. Users who care about these things will still tend to choose a non-Microsoft browser, and will continue to advocate the use of non-Microsoft browsers to others. Similarly, users who are stuck with Internet Explorer 6 for compatibility reasons have no salvation in Internet Explorer 8.