Firefox is slipping in its development schedule; Mozilla says it won't be able to release version 4.0 this year, and will have to delay the final version until early next year. "Completing this work is taking longer than initial estimates indicated as we track down regressions and sources of instability," the company said in a statement. "As part of our commitment to beta users, we will not ship software before it is ready."

The new schedule means that Beta 7 has been delayed till early November. Meanwhile, assuming everything goes according to plan, Beta 8 is set for November 12, Beta 9 is expected on November 26, and Beta 10 should arrive on December 10. "The frequent beta releases have been extremely helpful in identifying compatibility issues with existing web content, so we plan on continuing to release beta milestones through the end of December. Our estimate is now that release candidate builds will ship in early 2011, with a final release date close behind. Please note that, as always, this schedule is subject to change based on feedback from users and community members."

Firefox 4 was originally supposed to be released in June, but Mozilla keeps making changes to the browser. Currently, Firefox 4 is at Beta 6. Many believe version 4.0 is the only thing that can save the browser from a stagnating market share.