.header-bg:after {background-image: url('jpg/unknown-480x480.jpg');} @media (min-width: 30.01em) {.header-bg:after {background-image: url('jpg/unknown-960x480.jpg');}} @media (min-width: 60.01em) {.header-bg:after {background-image: url('jpg/unknown-1440x360.jpg');}} @media (min-width: 90.01em) {.header-bg:after {background-image: url('jpg/unknown-1920x480.jpg');}}