More CSS fixes (#1190)
More CSS fixes (#1190)

This fixes a regression in setting a header background.
mozilla/pontoon,jotes/pontoon,mathjazz/pontoon,mathjazz/pontoon,mathjazz/pontoon,mozilla/pontoon,mathjazz/pontoon,mathjazz/pontoon,jotes/pontoon,mozilla/pontoon,jotes/pontoon,jotes/pontoon,mozilla/pontoon,mozilla/pontoon