html {
    margin: 0;
    padding: 0;
}

body{
    background-image: url(fondoadrweb.jpg);
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    background-attachment: fixed;
}

@media only screen and (max-width: 600px) {
    body {
        background-image: url(fondoadrweb2.jpg);
        background-position: center;
        background-repeat: no-repeat;
        background-size: cover;
        background-attachment: fixed;
    }
  }