Thanks for reply. So, primarily, there is a empty, gray horizontal band directly below the navigation bar, the entire width of the window. It is about the same height as the navigation bar. That, and the missing menu bar, were the real issues that I noticed yesterday. The status bar at the bottom seems correct; it has my extension icons on the right, and displays loading addresses on the left. However, today I also noticed that, although multi-row_tabs.css has --multirow-n-rows: 3; which is what I wish, yet I'm only seeing two rows of tabs at the bottom--it appears that the third row of tabs is hidden behind the status bar?
My userChrome.css is quite simple: it calls my_appearance_settings.css to set tab colours, and it then calls, in order, your three styles: multi-row_tabs.css tabs_below_content_v2.css fake_statusbar_w_bookmarksbar.css
If I comment out the fake_statusbar_w_bookmarksbar.css line, then the statusbar is of course gone, and that gray band at the top now has the extension icons (although they are near the left end rather than the right). Also, there are now three rows of tabs, and the scrolling seems correct. So perhaps the fake statusbar style is interfering with the tabs styles?
Hope that information helps.