Did you feel that? Microsoft has shifted its Internet Explorer development team into higher gear and dropped another rev of the IE 9 beta, this one called Platform Preview Version 6 and touting "next generation experiences." It's all happening so fast. The new Platform Preview arrives just a few weeks after Microsoft launched a new full beta of Internet Explorer 9.

The days of rolling out a new revision every few years are long gone, as the battle for dominance among Web browsers is hotter than ever. Microsoft wants to keep its platform in the hearts of Web developers, and the simplest way to do that is to roll out newer, faster engines with more support for the new HTML5 features. Mozilla just released a new version of Firefox, claiming the fastest JavaScript performance. Google, once so shy that everything was an awe-shucks "beta," is now incrementing the version number practically every time a developer types "make." Google Chrome is up to version 7, and developers are sharing version 8.

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Does it make a difference that the version numbers are starting to turn as quickly as the National Debt clock? It depends upon who you are. The average Web surfer probably won't bother with Platform Preview 6 because it just shows off the rendering engine. It's only a rectangle for viewing Web pages. There are no extra buttons for juggling bookmarks or handling other browsing chores. As long as your mom or dad download a new version once or twice a year, they'll see that IE is getting zippier and the Web pages are becoming livelier.

Developers of Web pages, though, will notice several changes that illustrate how Microsoft is managing to catch up and even surpass the other browser development teams. The core engine is faster, and it is much more compliant with the HTML5 standards. While Microsoft once was content to develop its own standards and wait for the rest of the world to consider them, it's now battling to implement HTML5.

A quick survey of the features shows a steady devotion to implementing and, in some cases, extending HTML5 capabilities. The beta version of IE9 already implements some important features such as the Canvas and the video tags (H.264 only). Most of the new features in Platform Preview 6 seem to be in the area of document markup, with extra tags that illustrate the roles played. Where the HTML designer used to have to live with six types of headlines ( <h1> through <h6> ) and one type of paragraph, he or she can now include tags that indicate that some of the text comprises a <section> or an <aside> . Platform Preview 6 supports most of the standard elements, but not all; for example, it doesn't seem to be handling <time> yet. There's a nice demo of some of these HTML5 elements at Microsoft's website.

Some corners of Microsoft's spec are surprisingly deep. According to the W3C's HTML5 conformance tests, Platform Preview 6 implements 89.55 percent of the Canvas spec -- a significant accomplishment given that Google's Chrome 7 implements just 80.6 percent and Firefox 4 Beta 6 only 75.32 percent. I'm not sure how a browser can include 0.55 percent of a feature or how the W3C can measure this with four decimal points of precision, but I'm impressed by the depth and complexity of rendering options offered to the JavaScript programmer. These browsers aren't missing the ability to draw a line or a circle; they're now working on complex fills, shading, shadows, and compositing.

Microsoft is also highlighting its new CSS3 rules for rotating images, a feature it illustrates with a collection of images from Flickr that aren't bound to living parallel to the x-axis. Platform Preview 6 makes use of a Microsoft extra with the prefix "-ms-transform," the kind of eye candy that Microsoft hopes will encourage Web developers to build sites that are cooler when viewed in IE. To see the difference, try this first in IE9 beta, then with the Platform Preview. These sorts of extra features may be a way for Microsoft and other browser developers to build brand preferences with both content creators and users.

JavaScript performance continues to get faster across the board, and the numbers on the SunSpider JavaScript Benchmark show just how much IE9 has improved. My now ancient version of Internet Explorer 8 ran the benchmark in 11,653 milliseconds. Platform Preview 6 churned through it in 841 milliseconds. For comparison, I found that the IE9 beta, the best full browser available, clocked in at 1,084 milliseconds. Although this progress shows that Microsoft understands the importance of JavaScript performance, it also shows how far IE9 still needs to go. My version of Google Chrome ran the benchmark in 620 milliseconds.

In all, these JavaScript performance and HTML5 compatibility results show that Microsoft is pushing hard to produce a browser that's fast and behaves according to the modern standards. The company has watched the flight to other options, and now it wants to start giving users and developers reasons to choose IE first and foremost.

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