Header size

Hello! What size should the header image have? Also, you helped me a year ago to get a black line as a frame around a square on my frontpage - now the black frame is missing and the the square has turned white. Can you please help me get it back? See my website, it's the white square in the middle of the header where it say "kontakt". It shouldn't be filled with white, the square should just have a black frame www.inbe.se Thank you for your help, much appreciated. /Ingeborg