New security features have been included in the just-released Firefox 3.0 beta, although Mozilla has warned that most users should stick to Version 2.0 for the moment.

"We do not recommend that anyone other than developers and testers download the Firefox 3 Beta 1 milestone release," Mike Beltzner, the company's interface designer, said on Mozilla's website. "It is intended for testing purposes only."

But while the official word was for users to stand clear, Beltzner's personal recommendation was a lot less intimidating. "It's a preview release, so use with caution and don't expect your add-ons to work without some magic; but between you and me, I've been running on this 'developer preview' for at least three months, and have never looked back," he said on his own blog.

Beltzner touted several improvements in Firefox 3.0, including new security features, a redesign of bookmarking and history, but said they all require more testing and user feedback. The company has posted a more complete list of new features in the release notes on its website.

On the security side, Firefox 3.0 adds malware checking, an anti-phishing feature that warns users of suspicious URLs; one-click site information that displays site ownership; fixes for vulnerabilities in plug-in updating; and integration with anti-virus software and Windows Vista's parental control settings.

Mozilla also claimed that it has fixed more than 300 individual memory leaks and added a new cycle collector to eliminate other memory issues. Firefox has a reputation for consuming large quantities of memory the longer it's left running, and ultimately slowing down the computer, even though some of its developers have contested the claims, and even pegged the problem as one of perception.

Most current Firefox plug-ins will not work with Firefox 3.0, a stumbling block for some who might otherwise want to test the preview. "Users of the latest released version of Firefox should not expect their add-ons to work properly with this beta," the beta's release notes read.

Firefox 3.0 Beta 1 can be downloaded for Windows, Mac OS X and Linux in 21 language versions from Mozilla's site.

Mozilla has not set a deadline for delivering the final edition, and apparently does not intend to. "The final version of Firefox 3 will be released when we qualify the product as fully ready for our users," its release notes said. Mozilla is more than three months behind it own schedule schedule, in part because it extended the alpha-testing stage to encompass eight versions.

This summer, Mozilla pegged Beta 1's release for late July with a second beta in September, both to precede a final release by the end of the year. The company is now shooting to deliver a second beta before the end of the year, with more betas possible before producing one or more release candidates in a run-up to the final code.