Firefox: With the latest update, Firefox brought a brand new, Chrome-ish design. If you prefer the old look, you can get it back with a single extension.
Classic Theme Restorer replaces the new design with the old familiar look. The developer recommends starting over with a new profile, or alternatively deleting "localstore.rdf" from your profile folder to avoid any potential conflicts after upgrading from Firefox 28.
Classic Theme Restorer [Firefox Add-Ons]