Want to try IE 10? Not if you have Vista.

Microsoft unveiled its new IE 10 platform preview  at MIX 11 last week, but made no mention of the fact that it won't run on Windows Vista.

The platform preview isn't a complete browser and it only runs tests devised by Microsoft, demonstrating Web features. Still, only Windows 7 users can try it. The requirement to use Windows 7 is specified in the platform preview's release notes here.

Vista skippers likely won't care, but the Vista omission does highlight Microsoft's practice of tying its Web browsers to its Windows operating system lifecycles, and to particular versions of Windows. Because of this practice, IT pros maintaining a computing environment are compelled focus on both the Windows upgrade cycle and the Internet Explorer browser upgrade cycle, which is why it's important to note IE 10's restriction at this point to just Windows 7.

Many organizations still running Windows XP likely are vexed in retrospect by Microsoft's lifecycle approach, which entails time and costs for them. So, for instance, Windows XP and IE 6 both have the same software lifecycle. They both lose "extended support," as well as free security patch support, in April 2014. For companies that built their Web applications around the quirks associated with IE 6, the ending of such support can entail a mad scramble to get things updated; others may pay Microsoft for "custom support" or pay for independent software vendor help to manage the transition.

ZDNet blogger Ed Bott speculates that the ending of Vista's mainstream support on April 10, 2012 is the reason why IE 10 isn't supported on Vista. Possibly, IE 10 will be released to the Web a year from now, right when Vista will be showing its first terminal signs in Microsoft's software lifecycle. Microsoft apparently associates its IE lifecycles with the initial lifecycle stages of its Windows operating systems. Presumably, that's why IE 10 won't run on Vista, but there's no explanation so far from Microsoft.

Standards-based browser

Microsoft made the case that it had turned over a new leaf from its IE 6 days when it began its year-long effort to develop the current IE 9 browser, which taps into developing HTML 5 Working Draft specifications. The benefits of establishing an HTML 5 standards-compliant browser include a "write once, run anywhere" approach that Microsoft has been promoting in its marketing. Developers will be freed from writing to the quirks of a particular browser, which was a major impediment with IE 6.

If all popular browsers will be built to take advantage of HTML 5, browser choice might just depend on user preference. However, Microsoft has been promoting the idea that IE 9 and IE 10 on Windows 7 will be different from the competition. One of the features the company tends to promote is the ability to pin Web sites to the bottom of the IE 9 browser, which is a Windows-like feature.

Of course, other browser-makers also have tapped the HTML 5 specs. Apple, Google, Mozilla and Opera use those specs and write their browsers to serve multiple OS platforms. Microsoft, which just writes IE for Windows (and specific versions at that), consequently has fewer technical challenges to overcome. Dean Hachamovitch, Microsoft's corporate vice president for Internet Explorer, even cited the graphics and security limitations in Windows XP as reasons why Microsoft decided not to design IE 9 for that OS.

"Native" HTML 5 support

Hachamovitch also claimed that "the only native experience of the Web and HTML5 today is on Windows 7 with IE9." This view, which strangely omits any mention of IE 9 running on Vista, was echoed by Ryan Gavin, senior director of Internet Explorer business and marketing, in a blog post. If there is a reason why IE 9 on Vista would entail a less "native" HTML 5 experience, it isn't explained by Hachamovitch and Gavin. IE 9 is capable of running on both Vista and Windows 7.

By "native," Microsoft apparently means that IE 9 will allow users to run HTML 5-encoded video in the browser without requiring an Adobe Flash or Microsoft Silverlight add-on. Microsoft has publicized an ambiguous message about its own Silverlight platform even as it pushes the HTML 5 standardization message. The conclusion seems to be that developers will either use HTML 5, Flash or Silverlight depending on which tool works best. In the past, analysts have suggested that HTML 5 might work well for light graphics use, while Flash or Silverlight might be required to create richer Internet applications, but it's not really clear.

Microsoft's native HTML 5 claims have elicited ridicule from other browser makers. A Computerworld article tracked a number of sarcastic blog posts from Mozilla and Opera, for instance. The idea is that "native" HTML 5 is just marketing fluff.

HTML 5 is still at the Working Draft stage at the Worldwide Web Consortium. Giorgio Sardo, a Microsoft senior technical evangelist, estimated in November that HTML 5 would be "expected to go to Last Call (kind of feature complete) in the first 2-3 months of 2011." However, according to the W3C's Web site, HTML 5 is still at the Working Draft stage.