The newest beta includes fewer major changes than its Dec. 22 predecessor, with just a pair of performance improvements -- one to the code that handles the browser's bookmarks and history list -- called out by Mozilla.

According to Mozilla, Beta 9 sports 662 bug fixes or changes, less than half of the 1,400 it made in , which launched a little over three weeks ago.

Although Mozilla picked up the pace between Beta 8 and 9 -- the interval between Beta 7 and 8 was six weeks -- the company is pushing developers to get the code in shape for a "release candidate," the last major milestone before the browser is deemed good enough to officially ship.

Earlier this week, Mozilla's head of platform engineering said there were still too many "hard blocker" bugs -- flaws that would prevent Firefox 4 from final release -- and urged developers to toward a February finish line.

In a Thursday, Johnathan Nightingale, the director of Firefox development, called on all programmers to reevaluate their blocking bugs.