A Microsoft representative previews the &39'Foursquare Playground&39' HTML5 site in the new Internet Explorer 9.

AUSTIN, Texas--Just one year after it initially previewed its new Internet Explorer 9 browser, Microsoft formally launched the software today at the South by Southwest Interactive Festival (SXSW), bringing in representatives from launch partners from The Huffington Post, Foursquare, Groupon, and Pandora to demonstrate an experience that looks less like the Web as we know it and more like the app ecosystem of a smartphone or tablet.

"We're used to the Web getting better because of everything other than the PC," Internet Explorer's Dean Hachamovitch said of how the most innovative kinds of Web development have, of late, been for mobile and tablet platforms. Thanks to higher optimization for HTML5 and the ability to take advantage of more processor power, he said that IE9, which goes live later on Monday, will "bring all the benefits of a modern PC with Windows to browsing the Web."

Microsoft representatives previewed the IE9-optimized version of Foursquare, the geolocation app that's been ubiquitous at SXSW this year (again) and has built "Foursquare Playground," a new Web application that uses an animated HTML5 3D map that can sense the user's location, display locations with high levels of Foursquare activity, and offer a business search that can jump out into Bing Maps (which already has a notable Foursquare partnership in place).

These HTML5 sites are able to be as rich as they are because of hardware acceleration, which fuels the browser with the power of the graphics processing unit (GPU) as well as the central processing unit (CPU). They demonstrated the same HTML5 site--a graphics-intensive music archive for Seattle rock station KEXP--on both a Windows computer running IE9 and a MacBook Pro running Firefox. The Firefox browser, not surprisingly, was considerably slower in the demonstration, as was Google Chrome running on a MacBook in a later demonstration.

While Microsoft Internet Explorer still has powerful market share in the mainstream, tech industry professionals have long since abandoned its lackluster earlier versions for the likes of Chrome, Firefox, and Safari. But IE9 won't be compatible with the older Microsoft XP operating system, which still runs on 40 to 50 percent of Windows PCs.

The unveiling was held at a ballroom at the W Hotel in Austin, where the walls were decorated with the logos of the brands and companies that have partnered for "pinned" sites--logos that look suspiciously similar to iOS app icons. Tweaking and "pinning" a site for IE9 can result in a 50 percent jump in user engagement, Microsoft representatives said.

Web cult hero Ze Frank, a SXSW regular, joined the IE9 team onstage to preview his new application, Star.me, which was one of the featured launch partners. He hyped up HTML5 browsers, specifically IE9, as being able to bring back the "sense of discovery and play" that characterized the Web in its earliest days. Star.me, he said, is "like a social game meets a social network where you're kind of in kindergarten but just had a lot of espresso" by awarding cartoon "stars" to other Web users' profiles.

"Bringing these kinds of experiences back into the browser as a sort of a natural place for wondrous, joyous, experiences to start popping up again is awesome," Frank said, "and I think IE9 is a commitment to bringing that joy and wonder back into the browser and kind of back into the Web."

Not exactly a hardcore productivity app, but the stars are pretty cute.