Mitchell Baker has stepped down as the CEO of Mozilla, where she helped make the Firefox Web browser a potent rival to Microsoft's Internet Explorer.

Baker is handing over the CEO job to John Lilly, Mozilla's chief operating officer, who becomes responsible for pushing out the updates to Firefox and Mozilla's Thunderbird e-mail software, the company announced Monday. Baker will retain her role as chairman and stay active within the group, she said.

Baker has been with Mozilla since its inception. She was an attorney with Netscape Communications in the late 1990s when it created the Mozilla Organization, and she stayed with the group after AOL bought Netscape and helped to create the Mozilla Foundation in 2003.

Since then the open-source browser has built a worldwide market share of about 15%, according to estimates, and as high as 30% in some European markets. Mozilla says it now has 125 million Firefox users worldwide.

In a blog posting Monday, Baker said she'd been thinking for some time about the best way to use her time and about which of her duties could be handled equally well by someone else. Those duties, it turns out, are the day to day management of Mozilla's software, while Baker sees a wider role for herself in improving the Web experience for end users.

"I have a vision of the Internet and online life and a positive user experience -- and of Mozilla's role in creating these -- that is far broader than browsers, e-mail clients and even technology in general," she wrote.

She said she'll focus on efforts to make the Web standards process more effective, make security "understandable enough that people can protect themselves," and encourage more "hybrid" organizations like Mozilla -- "organizations which serve the public benefit but support themselves through revenue rather than fund-raising."

"I want Mozilla's influence on the industry to go beyond the bits we ship as software. More particularly, I want to use the impact Firefox gives us in the market to get openness, collaboration and user control embedded in other products, services and aspects of online life," she wrote.

Lilly, her replacement, will be focused on getting the next version of Mozilla's Web browser, Firefox 3, out of the door. He also wants to be more open about how Mozilla operates and how it will support itself in the future. "I’d like us to start talking more in public about how the future looks for Mozilla," he wrote on his blog.

Baker remains chairman of both the Mozilla Foundation, the non-profit side of the project, and the Mozilla Corporation, which was formed a few years ago to help raise funds and manage product releases.

"I've been involved in shipping Mozilla products since the dawn of time, and have no intention of distancing myself from our products or [Mozilla Corporation,]" Baker wrote.

The IDG News Service is a Network World affiliate.