@media only screen and (min-width: 769px) {
    img{display: block; height: auto; width: 900px;}
}
@media only screen and (min-width: 321px) and (max-width: 768px) {
    img{display: block; height: auto; width: 100%;}
}
@media only screen and (min-width: 0px) and (max-width: 320px){
    img{display: block; height: auto; width: 100%;}
}