Microsoft has broken its promise to support Web standards in the next version of Internet Explorer for Windows, according to the Web Standards Project - and the decision could have implications for Macintosh users and the future of the Web.

The Web Standards Project, a two-year-old coalition of developers and users that promotes the use of standards in Web-page development, accuses Microsoft of abandoning its promise to abide by World Wide Web Consortium (W3C) standards in Internet Explorer (IE) 5.5, which is due to ship in a few months.

Microsoft recently released the Macintosh version of the browser, which does support Web standards. The decision not to support the standards in the Windows version was condemned by a Web Standards Project spokesman as "very divisive" for the future of the Web, because developers who are compelled to write code for IE 5.5 will be leaving Linux, Unix, Netscape and Macintosh users out in the cold, while developers whose code complies with W3C standards will leave Windows users out in the cold.

Confused Jeffrey Zeldman, Web Standards Project group leader, said: "Microsoft, in its Macintosh Explorer division, did the right thing and said full implementation of CSS1 and HTML 4.0. We don't understand why they don't think Windows users deserve the same standard of standards compliance. If they could do it for their Macintosh group, surely they can afford to do it for the rest of the market."

The Web Standards Project said it is "incensed by Microsoft's arrogance" over a standards issue that is crucial to Web developers. This is because the dominant position of Microsoft's Windows operating system, into which IE has been integrated, will make it nearly impossible for developers to create documents that adhere to the W3C standards.

Shocked Zeldman said he was surprised to find out that IE 5.5 would not support the W3C standards that Microsoft agreed to support a few years ago. Most notably, Zeldman cited the planned lack of support for portions of cascading style sheets (CSS1), a standard established in 1996, and Document Object Model (DOM) 1 Core.

Zeldman said Microsoft's decision to depart from Web standards in Explorer 5.5 struck him as "bizarre and schizophrenic" because of the IE 5.5 version for Macintosh, which fully implements the CSS1 standard and HTML 4.0.

In addition to CSS1, HTML 4.0 and DOM 1 Core, the Web Standards Project supports implementation of XML 1.0 and ECMAScript, the standardized version of JavaScript, Zeldman said.