Marc Andreessen had no idea that the Mosaic browser he co-developed would kick off the Web revolution and become such an enduring and important piece of software.

Mosaic, created by Andreessen and Eric Bina at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, was "a renegade academic research project" aimed at universities and government contractors, he said.

At the time of Mosaic's release in 1993, the hot technology that was thought would change the world was interactive television and the availability of hundreds of channels, he said.

"We had extremely low expectations. And then of course it took off," Andreessen reminisced during a keynote session Thursday at Web 2.0 Expo in San Francisco during which he was interviewed on stage by John Battelle, chairman of Federated Media.

Of course, by the time he co-founded Netscape in 1994, Andreessen understood the potential of the Web browser, although he was in a minority among the skeptics in the industry and the media, he said.

Even today, when the Web is so widely considered a crucial element across most industries, it's interesting to find resistance to it and lack of understanding about how to leverage it, he said, citing media and telecommunication companies as examples.

Looking back, even Andreessen is surprised at the longevity and increasing impact of browsers on the Internet. "It turned out far better than anyone could have thought," he said.

Even elements that he thought would be quickly discarded as development progressed, like JavaScript, cookies and the back/forward buttons, have withstood the test of time, he said.

Far from nearing retirement, the browser is increasingly at the center of Web innovation, as more and more applications and services are built to be delivered via browsers, he said.

One clear example is social networking, which is, of course, browser-based and has displaced applications like instant messaging as the preferred communication method for young people, he said.

Perhaps unsurprisingly, Andreessen's latest venture, founded in 2004, is Ning, which provides a platform for anyone to create their own social network.

Ning currently hosts about 250,000 social networks, 70 percent of which are active, said Andreessen, Ning chairman and co-founder. The company has raised an eye-popping US$560 million from investors.

Asked by Battelle and later by an audience member to comment about competing against Microsoft and Bill Gates, Andreessen had no fighting words, despite the historic conflict between Microsoft and Netscape and the ensuing U.S. Department of Justice antitrust probe.

He said the IT industry wouldn't have experienced nearly as much growth as it has if Microsoft hadn't provided a standard operating system for PCs. He also praised recent moves by Microsoft to become more open in its technology.