Although the software leviathan's Internet Explorer easily reaches MSN, other browsers--such as Opera, Mozilla and some versions of Netscape--run into trouble.
Using the most recent browser from Mozilla.org to reach MSN brings a message from Microsoft saying it has "detected that the browser that you are using will not render MSN.com correctly." Mozilla.org does open-source browser development for AOL Time Warner's Netscape Communications unit.
"Additionally, you'll see the most advanced functionality of MSN.com only with the latest version of Microsoft Internet Explorer or MSN Explorer," the message continues.
The page then provides several links for users to download versions of Internet Explorer for Windows, Macintosh and MSN Explorer.
"All of our development work for the new MSN.com is...W3C standard," said Bob Visse, the director of MSN marketing, referring to the World Wide Web Consortium, which is developing industry standards for Web technologies. "For browsers that we know don't support those standards or that we can't insure will get a great experience for the customer, we do serve up a page that suggests that they upgrade to an IE browser that does support the" standards.
Norwegian browser maker Opera Software confirmed Thursday that it had noticed its browser is unable to access MSN.com. Several readers also alerted CNET News.com.
"Microsoft is actively keeping our browser from accessing MSN.com," said Jon S. von Tetzchner, Opera's chief executive. He added that every time a browser connects to a server, it sends a string to the server telling it what type of browser is seeking access.
"Microsoft is seeing (that) it is an Opera browser and shutting it out," said von Tetzchner, whose team was testing the problem Thursday. "If you change the Opera string by one letter, it is letting us in."
The software giant admitted that it is watching for Opera strings--but only because it wants to encourage people to use standard-compliant browsers.
"We do identify the string from the browser, and the only issue that we have is that the Opera browser doesn't support the latest XHTML standard," said Visse. "So we do suggest to those users that they go download a browser that does support the latest standards."
Earlier versions of the Netscape Navigator browser jammed and crashed when trying to reach MSN.com. The latest version, 6.1, seems to be working. Visse said MSN.com supports Netscape 4.7 and all later versions.
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A move to favoring Internet Explorer over other browsers would give Microsoft a considerable advantage as it prepares to jump into the world of Web services. Through its .Net software-as-a-service strategy, Microsoft hopes to sell software by subscription, and either directly or with a partner, offer a wide range of ancillary services, ranging from online calendars to financial and travel services.
Through Windows XP, MSN is emerging as a major end point for delivering those services. The majority of Microsoft's most popular products link to MSN.
Office XP, for example, features a pull-down, get-more-info menu feature called Smart Tags that connects to MSN. Microsoft had planned to include Smart Tags in Internet Explorer 6 but pulled the feature. Financial programs Money and Great Plains also lean heavily on MSN features. Besides launching MSN as the default home page, Internet Explorer 6 replaces the more typical "page not found" with an MSN search page.
Windows XP is chock full of MSN hooks. The Internet search feature from the Start Menu uses MSN. Windows Media Player drives traffic to MSN, as does the Passport authentication feature found in Windows Messenger. The Photo & Camera Wizard, where people can order online prints from digital images, also directs traffic to MSN.
Staff writer Joe Wilcox contributed to this report.