Microsoft's Internet Explorer 9 scored an early public relations victory when the first round of HTML5 compatibility tests from the World Wide Web Consortium had IE9 topping Google Chrome and Firefox.

However, W3C is warning against drawing any conclusions based on the early tests, saying thousands of more HTML5 tests are planned. The goal of the tests is not to declare one browser a winner, but rather to help vendors and Web application developers ensure interoperability across all browsers, W3C says.

"We do expect to have tens of thousands of tests," says Philippe Le Hegaret, who oversees HTML activities for the W3C.

So far, the consortium's HTML5 test suite contains 212 tests across seven types of feature categories. But another 1,000 tests are in the pipeline, waiting to be approved for the test suite. While the feature categories tested so far include attributes, audio, canvas, elements by classname, foreign content, video and XHTML5, the W3C will expand that list to include more categories. One area that hasn't been tested yet is Wweb forms, such as those you might use to type in credit card information.

Manpower limitations, and the fact that the HTML5 specification is still evolving, have so far kept testing from expanding to the extent that W3C envisions. Le Hegaret didn't put a timeline on his testing goals, but says the group is starting to receive more interest from browser vendors and users who can help submit test results and therefore speed the process up.

Even after the HTML5 tests reach the tens of thousands, there will still be limitations. For example, a video test would ensure compliance with the HTML5 specification but it wouldn't judge speed. "It doesn't tell you how well the video is being played," Le Hegaret says. "As long as the video is being played, that is enough for us."

While a separate web performance group within W3C does look at performance, the purpose of the HTML5 test suite is to help vendors and developers ensure that HTML5 applications work across all browsers. For example, a developer might check the test results before enabling a certain feature in an application, just to make sure it will work across IE9, Firefox, Chrome, Safari and Opera.

Developers can build HTML5 applications today, but they have to keep in mind that they are early adopters and act accordingly, Le Hegaret says.

"If you think HTML5 is perfectly stable today and you can use it without worrying about interoperability issues, I think you're going to fool yourself," he says.

Although the first round of HTML5 tests focused on desktop browsers, Le Hegaret says HTML5 compatibility is advancing more rapidly on mobile devices such as iPhones and Androids.

"We are in better shape on the mobile platform than we are on the desktop platform," he says. "The mobile market is upgrading more rapidly than the desktop market. But the desktop PC is catching up pretty rapidly."

See also: Adobe Illustrator gets HTML5 controls