Microsoft's Internet Explorer turns 15 years old this week. It's hard to think of a software application that's found itself at the center of more sector-changing drama: in addition to the seemingly never-ending browser wars, remember (how could we forget?) that the bundling of Internet Explorer with Windows was the fulcrum for the landmark United States v. Microsoft antitrust case.

Given its outsized position in peoples' Web lives--despite strong challenges from Firefox and Google Chrome, IE retains a lion's share of the browser market--it's easy to forget the browser's tiny stature upon its release in August 1995. At 1MB in size, and incapable of displaying graphics or newsgroups, Internet Explorer 1.0 could be forgiven for seeming like an afterthought; it came installed as part of the Internet Jumpstart Kit (subsequently Internet Connection Wizard), itself part of the Windows 95 Plus! Pack.

IE descended from an early Web browser named Mosaic, whose source code Microsoft licensed from a small company named Spyglass--which later filed a lawsuit over loss of royalties, once Redmond started giving away IE for free.

From that point on, though, the browser grew in complexity. The final version of IE 2.0, released in November 1995, supported newsgroups, cookies, Javascript, frames and the SSL (Secure Socket Layer). A little under a year later, Internet Explorer 3 featured support for .gifs and .jpg files, as well as MIDI sound files and streaming audio. By the time Internet Explorer 4 rolled around in 1997, the browser included another layer of multimedia features (Web Publishing Wizard, where are you now?)

In 1998, Microsoft found itself faced with antitrust action over the bundling of its Web browser with Windows. Microsoft argued that browser and operating system were mutually dependent, and eventually reached a settlement with the Department of Justice in 2001. But the case's effects continue to reverberate, in subtle ways; Microsoft executives' continual use of the word "choice" when describing any new initiative ("we realize customers have a choice") is one of those, I suspect.

Even with the publicity surrounding antitrust case, though, Internet Explorer continued to hold a dominant market position (Netscape had been thoroughly pulverized by that point). It was only until the rise of Firefox, along with challenges from Google Chrome and other browsers, that IE's share has been seriously threatened.

Then again, not that threatened--at least, not yet. Net Applications estimated IE's July market share at 60.74 percent, an increase from June's 60.32 percent. At the same time, the analysis firm estimated Firefox's share at 22.91 percent, Chrome at 7.16 percent, Safari at 5.09 percent, and Opera at 2.45 percent.

If IE's own history proves anything, though, it's that things change. Microsoft will launch its public beta of Internet Explorer 9 on Sept. 15, in a high-profile event in San Francisco; their hope is that the browser's improvements--which reportedly include speedier browser performance, greater compatibility and compliance with standards, and enhanced HTML5 support--will allow it to retain that market share for some time to come.