Microsoft's blockage of competing Web browsers from MSN.com has been good news for some plucky rivals: they are experiencing record traffic and downloads, and a leading Internet authority is heaping scorn on the software giant. Last week, people who tried to visit MSN.com with a non-Microsoft browser found themselves locked out . Although Microsoft's own Internet Explorer easily accessed the popular site, other browsers--such as Opera, Mozilla, Amaya and some versions of Netscape--received error messages and recommended that people "upgrade" to Internet Explorer. Intentional or not, the incident has been a fiasco for Microsoft. Criticism has come not only from the software giant's well-known critics but from a key figure in the normally impartial circles of the Internet standards-making community: World Wide Web Consortium (W3C) director Tim Berners-Lee. "Obviously this was a blatant attempt to use the leverage of some content to produce domination at the software layer," Berners-Lee wrote in an e-mail interview with CNET News.com on Wednesday. Web standards have been at the centre of the imbroglio, with Microsoft and competing browser makers trading charges that their products don't conform to W3C guidelines. Last week, a Microsoft executive blamed the error on non-Microsoft browsers, insisting that those browsers don't support W3C standards. That prompted technology leaders to lash out against Microsoft, saying the software giant was again violating antitrust laws by forcing people to abandon non-Microsoft browsers for access to all Web pages. Hours later, Microsoft pulled an about-face and opened a redesigned MSN.com Web site to some third-party browsers. Bob Visse, director of marketing for MSN, reiterated Wednesday that the block was an "error" and that Microsoft "took immediate steps to correct that mistake," though some non-Microsoft browser users are still having difficulty viewing MSN.com. The oversight has inflamed Microsoft critics, who question whether the incident was unintended and wonder whether it was a move to further the software giant's dominant position on the Internet. The incident happened the same day as the touted launch of Windows XP, Microsoft's newest operating system. Microsoft executives have made it a priority to expand the company's Internet strategy through the new OS. Despite Microsoft critics' suspicion about the reason behind the browser lockout -- and its timing -- the incident had an unintended consequence: it became a selling point for competing browsers. The dispute made headlines in newspapers around the world and was covered by Web sites in multiple languages with links to competing browsers, resulting in a torrent of new customers for the smaller companies. "In a way, Microsoft shot itself in the foot," Opera Software spokeswoman Katherine Barrios said Wednesday. "It's stirring up controversy -- and it's stirring up a lot of customers. People are a bit pissed off." Although the Oslo, Norway-based company did not supply specific numbers, Barrios said it had more site views and downloads of its free, advertising-supported Opera 5 browser on Tuesday than on any other day in its seven-year history. Opera wouldn't divulge exactly how many new customers it has added in the past week, but any incremental boost would add momentum to the company. Founded by former Norwegian telecom employees Jon S. von Tetzchner and Geir Ivarsoy, Opera has also seen a big spike in paid orders since the Microsoft block. Advanced Opera browsers range from $20 for students and senior citizens to $39 for most individual buyers. In May, the company announced that it would supply IBM's Internet appliances with browser software, and it had previous deals with Advanced Micro Devices, Ericsson, Psion and Be. Still, Opera and others face a daunting nemesis: Internet Explorer has more than 80 percent of the browser market, dwarfing its rivals. Netscape holds about 13 percent, while Opera, Mozilla and Amaya -- which caters to individual and corporate Web designers -- make up the rest. Amaya was developed by Web technologists at the Massachusetts Institute of Technology (MIT) and lets people read and edit sites simultaneously. Amaya released new software at the same time as the Microsoft flap last week, so developers there are reluctant to credit the software giant exclusively for increased downloads. MIT also publishes an obscure "validator" used to screen whether sites comply with W3C standards, and the site received a flood of use from people eager to test MSN.com's compliance. On 24 October, before the MSN.com block, 11 people checked site standards through the W3C's HTML Validation Service. On 25 October, the day CNET News.com first reported the issue, 4,128 people tested standards. The following day, 16,732 people tested standards. The squabble also prompted an outcry from Berners-Lee, who holds the 3Com Founders Chair at the Laboratory for Computer Science at MIT. His response was surprising, given that Microsoft is a member of the W3C and the consortium has an unofficial policy of refraining from singling out individual members. Berners-Lee wrote the first Web client and server in 1990 and is credited with creating the World Wide Web. "I have fought since the beginning of the Web for its openness: that anyone can read Web pages with any software running on any hardware," he wrote in response to written questions. "This is what makes the Web itself. This is the environment into which so many people have invested so much energy and creativity. When I see any Web site claim to be only readable using particular hardware or software, I cringe -- they are pining for the bad old days when each piece of information needed a different program to access it." The incident is still fanning anger in the technology industry, largely because Microsoft hasn't completely fixed its alleged error. Although people using non-Microsoft browsers are not entirely locked out as they were last week, some browsers are still having difficulties on MSN.com. Trying to view MSN.com through Opera results in oversized fonts and improper formatting. The problem involved an issue with MSN.com's "cascading style sheets," rendering them slightly off when viewed through Opera. Cascading style sheets automate the task of changing the style and layout of multiple Web pages, so that one change flows through to all related pages, much like a template. Viewing the same page through Amaya results in odd colours that render some text unreadable. Janet Daly, head of communications for MIT, was cautious about blaming Microsoft, noting that sometimes colors aren't always rendered perfectly on sites other than MSN.com. Berners-Lee sounded a more critical note. "Control over a person's desktop and their browser is control over their whole Net-mediated perception of the world out there," he wrote. "It is very powerful.