The only effects the header, associated menus, and the search box. It doesn't change the map or any editor. The search box will be transparent when it doesn't have the focus and the mouse isn't overhead. The border around the search form will be gone. Menu buttons in the header are light grey (#eee) normally and a darker grey (#aaa) when the mouse is overhead or they have the focus. Items in dropdown menus also get a gray theme. They will be light grey (#eee) when the mouse is overhead or they have the focus. The inbox counter will be light grey (#eee) with a darker grey border (#333) when the mouse is over that link or the link has the focus.