Except Tree Style Tabs makes Firefox 29 look very bad. For some reason, it causes the top part of the chrome to be two shades of gray. The area with the title,

Except Tree Style Tabs makes Firefox 29 look very bad. For some reason, it causes the top part of the chrome to be two shades of gray. The area with the title, and minimize maximize buttons, its one shade, and then the area with the address bar and buttons is another shade of gray. With a harsh line where the two areas meet and are a different color.