The tab bar doesn't have a border below the active tab, and the lack of a unified border (similar to the non-GTK one in FF2) causes the GTK tabs to overflow into the page view by one pixel (this may be theme dependent).
In a strictly technical sense, this is not a bug, since it's exactly how other GTK tabs behave, but the abrupt transition it causes is visually displeasing, so I think it should pass as an UI bug. The look and feel it causes is unprofessional, and the fact that other projects (such as Epiphany) inherit the same behavior shouldn't be a reason not to fix it in Firefox, if technically feasible.
Binary package hint: firefox-3.0
The tab bar doesn't have a border below the active tab, and the lack of a unified border (similar to the non-GTK one in FF2) causes the GTK tabs to overflow into the page view by one pixel (this may be theme dependent).
In a strictly technical sense, this is not a bug, since it's exactly how other GTK tabs behave, but the abrupt transition it causes is visually displeasing, so I think it should pass as an UI bug. The look and feel it causes is unprofessional, and the fact that other projects (such as Epiphany) inherit the same behavior shouldn't be a reason not to fix it in Firefox, if technically feasible.