The success of alternative browsers such as Firefox will cause Microsoft to be even more aggressive in holding onto its virtual Explorer monopoly, the founder of Netscape Marc Andreessen has predicted.

Netscape's market-leading Navigator browser was squashed by Microsoft Internet Explorer in the 1990s after the software giant tied it in with its Windows OS. Its automatic inclusion sparked the anti-trust investigations into Microsoft.

As a result of the new monopoly browser innovation at Microsoft "pretty much stopped in 1998", Andreessen said during a session at the Web 2.0 conference in San Francisco yesterday. The result has been that Microsoft has missed the opportunity to promote other products and allowed competitors to get a foot in the door.

"One of the most amazing things over the last six or seven years is watching Microsoft basically get a monopoly over the browser and then not use it," Andreessen went on.

Explorer has been used by approximately 95 percent of Web users since June 2002. Recently, however, its dominance has begun to erode, due in part to a number of well-publicised IE security vulnerabilities and a favorable reception to Firefox, a slimmed-down browser developed as part of the open-source Mozilla project.

Increasing pressure from alternative browsers such as Firefox and Opera will ultimately cause Microsoft to take a second look at the browser and how its monopoly can be used, Andreessen said. "Microsoft is certainly going to respond competitively to these things. I can guarantee that. I think that it is quite possible that this is going to get very interesting over the next two or three years."

Andreessen's comments came during a discussion with Yahoo COO Dan Rosensweig, in which they debated the future dynamics of Internet business. The two were at odds as to whether control over user data would become a major issue in the coming years, with Andreessen arguing that denying users control over their data ultimately would be a way of locking customers into "walled gardens" of Internet services.

The phenomenon can already be seen with companies such as eBay, he said. "You can't get your reputation out of eBay, you can't get your purchase history out of eBay, you can't get your stores out of eBay," he said. "It's a plantation owner/sharecropper kind of relationship."

Rosensweig, whose company has more than 150 million registered users, argued that consumers today have retained the ability to change their online habits. "We noticed a few people who changed their habits in the last few years in some categories," he said. "Search may be one. We're living in a world today where it's too easy to change."