On Thursday, Christian Legnitto, who oversees Firefox releases, said that Beta 12 would probably not ship for several days.

"The bugs blocking beta 12 are expected to be fixed in the next day or so," Legnitto said yesterday in a message to a . "At that point, we will freeze nightlies and then create the beta build when we are confident of quality."

As of Friday, on what Mozilla calls its "hard" blocker list -- those bugs that must be fixed before it deems Beta 12 good to go.

One of the five bugs is rated "critical," while another is ranked "major" and three are labeled "normal." Two of the remaining flaws are in Firefox's hardware acceleration code, which shifts some of the browser page rendering and composition chores from the CPU to the graphics processor.

Although Mozilla had once planned to ship Firefox 4 in November 2010, delays last fall forced it to announce in October that it would instead wrap up development .