@Matt 5

I think the point, based on my extremely hazy memory, is that a Ballmer or someone like that declared after IE6 that the browser as a product had basically reached its design conclusion and they didn't see any point in continuing active research and development. Following Firefox, Microsoft were suddenly talking up tabs and anti-phishing and other such interface enhancements.

I do take issue with: "Firefox’s presence was a large factor in Apple being able to ship a browser to its user base as the Mac came back to the market." Surely the main thing that made Apple feel willing to ship their own browser was Microsoft dropping IE for Mac?