html, body {
    height: 100%;
    width: 100%;
    padding: 0;
    margin: 0;
}

body { 
    background-image: url(../img/Tarifas.jpg);
    background-position: center center;
    background-attachment: fixed;
    background-size: 100% 100%;
    background-repeat: no-repeat;
}

@media only screen and (max-width: 320px) {
    #image { 
	background-image: url(../img/Tarifas_mobile.jpg); 
    }
}