Why Tabs are on Top in Firefox 4.0

Firefox 5 Beta will be here soon but Firefox 4 introduced a controversial change, which hopefully gets addressed in this next release!

With Firefox 4, Tabs are by default, positioned above the address bar! There were user testing done and have proved "that some people do feel comfortable with the new tab position as soon as they get used to it". As an option, users can check off this default setting with View>Toolbars> (check off) Tabs on Top, to get back to the 3.x look, which seems to make better sense.

Before commenting further, it is fair to understand the rationale (with a video) behind this change. The link even provided some of mockups you see used in the video. For your easy reference, below is a summarize excerpt from Sitepoint:

Mozilla cite four main reasons for their change of opinion:

1. The conceptual model: the address bar and controls apply to the current tab.
2. App tabs: like Chrome, Firefox 4.0 will allow you pin small regularly-used tabs to the tab bar. The address bar and other controls will be removed for these web applications.
3. Tab-based UI: Firefox 4.0 will show windows such as downloads and the bookmarks organizer in tabs. It makes no sense to have the address bar and other controls visible.
4. Notifications: some error and warning messages now appear below the address bar.

There are indeed some sound and valid reasons for the change. The repositioning of the tab might be a bit pre-mature since most users are still browsers rather than web app users. But why has this new tab position caused such a controversy to start with? The assumption that the address bar belongs to the tab is probably the basis of it all. It is not really a simple cognitive issue and it contradicts with our mental model of an address!

If an address belongs to a house, should we be seeing the house first or the address first? The address bar is a dynamic field and controls the content of the tab, it does not belong to the tab per se. From the video, it seems that the decision was made based on a layout issue rather than a UX design issue. There seemed no differentiation between dynamic and static fields, all fields are treated the same... static!

This is a very good example to illustrate the fine-line-decision-making in a multidisciplinary design team. And it is all these subtle factors that make user experience design a challenging and interesting job!