@media only screen and (max-width: 700px) {
    html, body {
        margin: 0;
        padding: 0;
        background-image: url('../Images/indexBG.jpg');
        background-repeat: no-repeat;
        background-attachment: fixed;
        background-size: 100% 100%;
    }
}

@media only screen and (min-width: 701px) {
    html, body {
        margin: 0;
        padding: 0;
        background-image: url('../Images/indexBG.jpg');
        background-repeat: no-repeat;
        background-attachment: fixed;
        background-size: 100% 100%;
    }
}