Despite the progress, Microsoft still lags behind other browser vendors in incorporating the latest standards, such as Scalable Vector Graphics (SVG), which is implemented in Firefox, Safari and Opera.
But with many parts of Internet Explorer in need of updating, Microsoft had to choose where to focus its attention when it developed IE8. "We tried to move everything forward across the board in IE8, but we picked one area we wanted to get right," and that was support for CSS 2.1, says Wilson.
Wilson's goal is to have a complete implementation of CSS 2.1 when IE8 finally ships. But the CSS 2.1 specification is still in the Candidate Recommendation stage. Wilson says IE's release will go forward next year whether CSS 2.1 is final or not.
He's confident, he adds, that there will be "minimal interoperability problems." If definitions do change in the final Recommendation, future versions of IE will change to support that, he says.
As with any other fully standards-compliant browser, IE8 will work on all Web sites that follow the standards -- and break when visiting sites that were designed to exploit the proprietary features and other idiosyncrasies of Internet Explorer 6 and 7. To fix that, Web site designers will either need to make their Web sites conform to standards or add a tag in the Web page header that tells IE8 to switch to IE7 behavior.
"Once that happens -- once sites that worked fine in old versions of IE start breaking -- the unwilling will get religion about Web standards," says Jeffrey Zeldman, executive creative director of the Web development firm Happy Cog and publisher of A List Apart , a Web site for developers.