Mozilla has set Friday as the ship date for the first preview edition of Firefox 3.1, the fast-track update it hopes to polish off by late this year or early in 2009.

In a meeting Tuesday, Mozilla developers and managers nailed down details of Firefox 3.1, including the release date for the first alpha. Previously, Mozilla had tentatively scheduled the alpha for sometime this month.

"Still on track for Friday release," said the notes posted online after the morning meeting.

Mozilla froze the Firefox 3.1 code Monday and will begin to assemble builds of the preview Tuesday, the notes continued. Only the US-English version of the browser will be tested before it's posted to Mozilla's servers.

Although the alpha is a work in progress -- numerous features Mozilla wants to ship with the final won't make it into the first preview -- several changes will debut Friday, including improvements to the location bar and enhanced Ctrl-Tab tab switching that presents thumbnails when cycling through open tabs.

The new Ctrl-Tab presentation and behaviour -- on the latter front, pressing Ctrl-Tab switches between current and last-viewed tabs rather than simply moving to the next tab to the right -- was, like many of the features slated for Firefox 3.1, originally meant to be included with Firefox 3.0.

In May, when Mike Schroepfer, Mozilla's chief engineer, first talked about Firefox 3.1, he said that the update would comprise features that didn't make it into the June release, but were "nearly complete."

The list of features being considered for 3.1 range from support for offline storage by Web apps to adding support for the Cross-Site XMLHttpRequest (Cross-Site XHR) specification, a still-under-development specification that Microsoft recently said it is also investigating.