body {
      background: url("/fileadmin/user_upload/Hintergrund/Filmball-Location.jpg") no-repeat center center;
      background-size:100% 100%;
      overflow-x: hidden;
      overflow-y: hidden;
    }
    
    @media only screen and (max-width: 767px),
    @media only screen and (max-width: 767px) and (orientation:landscape) {
       body {
         background: url("/fileadmin/user_upload/Hintergrund/Filmball-Gebaeude.jpg") no-repeat center center fixed;
         -webkit-background-size: cover;
         -moz-background-size: cover;
         -o-background-size: cover;
         background-size: cover;
      }
    }