Mozilla has made a preview of its next web browser - Firefox 3.5 - available to 800,000 Firefox 3.5 beta testers.

The software company said it was looking for community feedback on the preview, which now features fixes for a number of bugs in the browser and its JavaScript engine as well as improvements for video and audio playback.

Although not a release candidate, the preview is considered stable enough for daily browsing use, Mozilla said. Testing has not been completed to the point where the software could be declared a release candidate.

But a release candidate is due soon, with general availability expected later this summer. Previously, the company had anticipated a release candidate for the first week of June and general availability later this month. A Mozilla representative said the company is driven by quality rather than a timeline.

Firefox 3.5 features such highlights as video capabilities and support for private browsing, in which website visits are not recorded or saved to disk, said Vlad Vukicevic, tech lead for the Firefox project at Mozilla. But speed improvements are paramount, he stressed.

"The main significance [of the browser upgrade] is that Firefox 3.5 is really, really fast," Vukicevic said.

JavaScript performance is boosted via the TraceMonkey JavaScript engine.

Other features of Firefox 3.5 include HTML 5-based capabilities for audio and video, offline caching, and the HTML drag-and-drop API for moving items within and between websites. CSS enhancements, including downloadable fonts, also are featured.

Firefox 3.5 is the new name Mozilla gave to its 3.1 browser after developers said the '3.1' moniker didn't properly reflect the amount of new features and changes from last June's Firefox 3.0.

The preview offers video and audio capabilities based on the Ogg format.