User blog comment:Sarah Manley/Test the Expanded Wiki Navigation/@comment-168424-20111007212922/@comment-957747-20111007231601

Fandy, this is due to the new limitations Wikia placed on the width of the navigation. The 'wrapping' you're seeing is due to there not being enough space to show the tab. FF 3.6 apparently has a minimum font size or something different than 7.0 that increases the width of those tabs on top.