Is Mozilla Firefox the New IE:6?

I have for many years sworn by Firefox as the most dependable browser. After years of being sick to the hilt of Internet Explorer it was great to find something that really worked.
Just lately though, not sure when, Firefox seems to have slipped in its performance and ability. I am now finding Chrome to be the more reliable.
Firefox is now doing some of those odd rendering nightmares that was so common in IE6. (latest release).
Example. I am doing some long overdue updates on a website of mine and somewhere along the way something went to cock, maybe a missed closed div or a css error or something, I am not sure yet and still looking at it. But the front-page index alignment went wayward and he footer went south as displays as if no styling. Odd as I haven't touched the footer. Also very strange though as both Chrome and Safari don't see the issue and render the page as should be.
It's likely to keep changing as I work through it but please see and tell me if your seeing an unstyled footer area with the WPMUDEV logo in it? And what browser you used.
So is Firefox the next IE6?????