Following the release of the beta 10 of Firefox 4, we were expecting one more beta before hitting the Release Candidate (RC) stage, but bugs, including one related to the Microsoft Hotmail service, it seems that we are going to be treated to at least two more betas.
But what's interesting here is that this isn't a Firefox bug, it's a problem with the Hotmail code causing an HTML5 incompatibility. Mozilla isn't willing to code around this issue just for Hotmail so is planning to wait for Microsoft to fix the code before releasing Firefox 4. Since Mozilla are having to rely on a third-party to fix the problem, there's a lot of uncertainty as to how long it could take.
Mozilla is doing the right thing in delaying Firefox 4 over this issue, and right for not coding around the problem, but this is yet another Firefox 4 delay, and one that's likely to push the browser out towards the end of February, or even March. This loss of momentum is bad for Firefox, and good for Chrome and Internet Explorer.