Mozilla on Monday released Firefox 3.1 Beta 2, an update to its popular Internet browser.

The company characterizes the software as a preview release for developer testing. It's available for Windows, Mac OS X, and Linux in 54 languages.

The updated browser includes the New Private Browsing Mode, which allows users to surf the Web without leaving locally stored records of online activities. A number of news organizations, including InformationWeek, have referred to this as "Porn Mode," named so because it's widely believed that this feature is used for surfing porn sites.

In a comment posted on an article last month about the development of this release, Mike Beltzner, director of Firefox at Mozilla, dismissed that term. "At this point, I think the only people who are commonly referring to this feature as 'Porn Mode' are headline writers looking to attract attention," he wrote.

Mozilla suggests that Private Browsing Mode is "perfect for online holiday shopping!"

Replying to an e-mail to confirm that he had in fact authored that comment, Beltzner said he was frustrated with the term "Porn Mode" and that he believes it marginalizes useful cases for browsing without leaving local tracks.

Firefox 3.1 Beta 2 also features enhancements to the Clear Private Data tool, which helps make it easier to remove data about online activities that occurred when Private Browsing Mode wasn't turned on.

The new TraceMonkey JavaScript engine has been turned on, promising a substantial speed improvement when browsing any site that uses JavaScript. Mozilla claims that the Gecko rendering engine has been improved too.

There's also support for new Web technologies, including the HTML scripting for video and audio elements, the W3C Geolocation API, JavaScript query selectors, CSS 2.1 and 3 properties, SVG transformations, and offline applications.

Firefox reached a major milestone last month when it broke the 20% mark for worldwide market share, based on Net Applications data. At the same time, it faces renewed competition from Apple, Google, and Microsoft, which all see their respective browsers -- Safari, Chrome, and Internet Explorer -- as critical components of their software stacks.

The final version of Firefox 3.1 is expected next year.