The problem is that many Web developers create their sites so they work best with Internet Explorer (IE), but not to work as well with browser software used by relatively tiny groups of potential visitors.
Sites subject to complaints from Firefox users include Web travel site Expedia and Microsoft's MSNBC news site. Even Shutterfly, the online photo service backed by Netscape Communications co-founder Jim Clark, warns visitors that it supports only a limited set of browsers.
These incompatibilities between browsers are as big a headache for developers as they are for Web surfers, some professionals say.
"It's definitely a problem," said Noel Briggs, a developer at Web design company NetTensity. "The time we waste on addressing browser incompatibility problems easily amounts to a significant percentage of our payroll."
The biggest reason why most people can't dump IE, however, is Microsoft itself: The software giant's Windows Update site blocks out non-IE browsers completely. That means anyone running Windows who wants to download and install the latest security updates from the Web will have to keep IE close at hand. Some consider that ironic or worse, given that authoritative groups such as Carnegie Mellon University's Computer Emergency Response Team now warn people to stay away from IE because of its myriad security problems.
While some people are downloading alternate browsers out of frustration with IE, which last had a significant upgrade three years ago, others may be swayed by grassroots Internet campaigns urging Web surfers to dump IE.
These include the Web Standards Project's Browse Happy site and the Mozilla Foundation's volunteer-based marketing site, Spread Firefox, which it launched alongside the preview release of Firefox 1.0.
Most IE alternatives support World Wide Web Consortium (W3C) standards, which give Web developers all the tools necessary to build fully compatible sites. Nevertheless, Microsoft has created proprietary elements within IE to support some enhanced Web page features, such as multimedia. Web developers who decide to use these features may effectively lock out surfers who use non-IE browsers.
Corporate Web developers frequently write code to work with IE rather than to Web standards, because their clients want to use Microsoft's proprietary CRM (customer relationship management) and ERP (enterprise resource planning) features. Since IE dominates the market so thoroughly, some companies simply balk at the cost of tests that would help ensure cross-browser compatibility.
The situation has some Web developers shaking their heads in disbelief.
"Sites as large as Expedia and MSNBC should be able to cater to just about everybody who wishes to use the site," Briggs said. "If certain TVs weren't able to reliably render the MSNBC cable news channel, I am sure that the network would take the issue seriously."
News.com writer Paul Festa contributed to this report.