Firefox 3.0.9 may not be the only update Mozilla unveils this week; the company is still planning on releasing Firefox 3.5 Beta 4 by the end of the week, according to posted meeting notes. That schedule may slip, however, as Mozilla developers have yet to declare a "code freeze," a milestone that means all the bugs that will be fixed have been. There are currently seven bugs that must be resolved before the beta can move into internal testing prior to actual release.

In a note from a , Mozilla said that a code freeze for Firefox 3.5 Beta 4 was "day-by-day." Beta 4 has already slipped from an earlier schedule that said it would ship by April 14.

Firefox 3.5, , was conceived as a "fast track" upgrade last year, and was originally intended to launch in late 2008. But the browser's progress has been repeatedly delayed, either to add new features, as was done last fall, or to deal with troublesome bugs. As a result, Mozilla has had to rework 3.5's schedule several times. , the most recent update to Firefox 3.5, shipped March 12.

can be downloaded for Windows, Mac OS X and Linux from the Mozilla site. Current users can also call up their browser's built-in updater, or wait for the automatic update notification, which should pop up in the next 48 hours.