Microsoft is working to fix a "technical glitch" that blocked non-Microsoft browsers accessing the MSN.com portal yesterday.

The problems occurred when Microsoft posted a redesigned site to mark the launch of its new operating system, Windows XP. People, using non-Microsoft browsers, who tried to visit encountered difficulties because the company had not provided support for them. The Opera browser, Mozilla, HotJava and earlier versions of Netscape were affected.

Non-Microsoft browsers encounter the following error message: "Attention: Web Browser Upgrade Required to View MSN.com. If you are seeing this page, we have detected that the browser that you are using will not render MSN.com correctly. Additionally, you'll see the most advanced functionality of MSN.com only with the latest version of Microsoft Internet Explorer or MSN Explorer."

Browser fix Microsoft is working to fix the problem and should provide access to all of the browsers by the end of today, an MSN representative said.

The company said the problem occurs when using a browser that does not support XHTML (Extensible Hypertext Markup Language), a standard set by the World Wide Web Consortium (W3C).

"The more closely that Opera and Mozilla support the latest standards for XHTML, the better experience customers will receive," the representative said.

Microsoft said that although Mozilla and Opera users will be able to access the site in the future, they will continue to have a "degraded experience" because the browsers do not support XHTML.

Jon von Tetzchner, Opera Software CEO angrily refuted Microsoft's allegations. He said: "Opera's XHTML standard is of the highest quality. In fact, Opera is internationally acclaimed and renowned for its strict compliance with all international Internet standards."