After leaving much of the matter of creating a new version of HTML to Apple, Google, Opera, and Mozilla, Microsoft has begun sinking its teeth into the Web standard.

The move adds clout to the effort to renovate HyperText Markup Language, the standard used to describe Web pages, which last was formally updated in 1999. In a mailing list posting on Friday, the software giant offered a host of questions and concerns with the present proposal.

"As part of our planning for future work, the IE team is reviewing the current editor's draft of the HTML5 spec and gathering our thoughts. We want to share our feedback and discuss this in the working group," said Internet Explorer Program Manager Adrian Bateman in the message. "I will post our notes as we collect them so we can iterate on our thinking more quickly. At this stage we have more questions than answers, but I believe that discussing them in public is the best way to make progress."

HTML 5 in its current draft form includes a number of significant advancements, notably several that make the Web a better foundation for applications, not just static Web pages. Among the present HTML 5 features are built-in video and audio, the ability to store data on a local computer to enable use of Web applications even when offline, Web Workers that can perform computational chores in the background without bogging down Web application responsiveness, Canvas for creating sophisticated two-dimensional graphics, and drag-and-drop for better Web application user interfaces.

The formal HTML standard is under the governance of the World Wide Web Consortium (W3C), and Microsoft's Chris Wilson is a co-chairman of the W3C group developing HTML. But much of the course of HTML 5 has been set so far outside that by a separate effort called the Web Hypertext Application Technology Working Group (WHATWG), which browser makers launched years ago when they didn't like the XHTML 2.0 direction the W3C was trying to take HTML.

Microsoft hasn't been uninvolved in HTML 5. It's the origin of technology in HTML 5 called ContentEditable, which lets elements of Web pages be edited in place by people using a browser. And Microsoft said its newest browser, Internet Explorer 8, also supports these HTML 5 components: the DOM Store, Cross Document Messaging, Cross Domain Messaging, and Ajax Navigation.

But the new message indicates Microsoft is getting serious about the effort, digging into many nitty-gritty aspects of the proposed specification. That's important because Microsoft has of late embraced a standard-centric philosophy when it comes to what technology IE supports, and IE is of course the dominant browser on the market.

Microsoft declined to comment for this story.

Google, Apple, and Mozilla have been trumpeting HTML 5 features in their latest browsers, but Microsoft takes a more cautious tone.

"The support of ratified standards (that Web developers) can use is something that we are extremely supportive of," said Amy Barzdukas, general manager for IE, in a July interview. "In some cases, it can be premature to start claiming support for standards that are not yet in fact standards."