body{
    background-image: url("../image/bg_mobile.jpg");
    background-position: center;
    background-size: cover;
}

a{
    text-decoration: none;
}
@media screen and (min-width:768px) {
    body {
        background: url("../image/bg_pc.jpg") #0b263b no-repeat center top;
    }
}