Windows border has come back when not maximised
When firefox is maximised the orange firefox button is at the top left with the tabs to the right. When firefox is in a window the orange firefox button is at the top left with the tabs below. In both these instances the theme is all around the window and no "windows" borders are present.
By accident I have managed to get the standard blue "windows" border to return to firefox when it is not maximised and the orange firefox button is in this "windows" titlebar but the theme no longer is in this area. How have I done this and how can I change it back to remove the "windows" theme titlebar?