#bg {
    width: 100%;
    height: 100%;
    position: fixed;
    top: 0;
    left: 0;
    z-index: 0;
    background-image: url("covid.jpg");
    background-repeat:no-repeat;
    background-position: center center;
    /* background-attachment: fixed; removed for Android */
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}