In the Firefox 4 nightly builds, and in Firefox 4 Beta 1, we are changing the default tab position so that tabs are on top. This is a preference that users can change by right clicking on any of their toolbars. Moving the default tab position is obviously a significant and to some extent controversial change to the Firefox UI, which is why we made the video above to help explain our rationale.

Contributors who are active in the Mozilla community will know that this debate literally goes back for years. So in some respects this video will serve as quick summary of all of the different arguments both for an against the change. But the more interesting part isn’t about looking back, it’s about looking forward. Recently modern browsers have been transitioning to placing tops on top, and that decision isn’t arbitrary, it isn’t about fashion. The change to placing tabs on top isn’t about one browser versus another browser, it’s about the evolution of the Web as a platform. Read the rest at Alex Faaborg’s Blog.