Struggling to close the gap in its war with Microsoft, Mozilla.org has released a preview of its first full-featured Web browser.

Mozilla, founded by Netscape Communications to handle the open source development of the Communicator browser, is referring to the release merely as the "M12 build." But after review by Mozilla contributors and other followers, the build may gain "alpha" status, a term normally reserved for the first official trial version of a product.

"It's not definitively an alpha," said Mitchell Baker, whose title is "chief lizard wrangler" for Mozilla.org. "Alpha means a lot of things to a lot of people. Our goal in putting out an alpha is to label it as something that someone can use regularly for their browser and mail client."

Mozilla's releases are distinct from Netscape's. Netscape, which was acquired by America Online last year, will put out a Netscape-branded version of the browser, including releasing its own initial alpha and intermediate beta trial versions. Both Netscape and Mozilla.org declined to give target dates for those releases.

Communicator has faced a series of delays on its way to market, fueling Microsoft's ride to overtake Netscape in the browser market.

For version 5.0, Mozilla has been rebuilding Communicator from the ground up, creating a browser made of separable components that hews closely to industry standards recommended by the World Wide Web Consortium (W3C).

Communicator 5.0 is based on Gecko, the Communicator browsing engine responsible for rendering graphics and text.

Notably, it uses Extensible User Interface Language (XUL), a new technology for creating the user interface with Web programming languages, rather than computer coding languages. XUL is expected to make it easier for developers to create Mozilla-based browsers for multiple computer operating systems.

"This release is in many ways a breakthrough product compared to the older browser," said Chris Saito, senior director of client product marketing for Netscape. "It's...designed to be very small from a download perspective, and it's faster than the older browser. It has the best standards support of any commercial browser out there across all different platforms supported on Mozilla.org, including Windows, Macintosh, Linux and several other Unix versions."

Differences between the Mozilla browser and the one that Netscape will ultimately ship are already apparent. Mozilla's, for instance, features an instant messaging client that ostensibly would compete with AOL's market-leading AOL Instant Messenger. And Saito promised instant messaging innovations from Netscape in version 5.0, though he declined to discuss them.

Sources have said Netscape plans to further integrate its email and instant messaging applications.

One of Mozilla's chief problems as an open source project has been its failure to rally large numbers of developers outside Netscape to chip in with coding, bug-hunting and other tasks.

But lizard-wrangler Baker said the number of non-Netscape contributors to Mozilla has increased "dramatically."

Baker cited a decision by Intel and Nokia to use Mozilla's Gecko browser engine in Internet-enhanced television products. The products use the open source Linux operating system and are expected to launch in the second half of 2000.