#mainDiv {   
    background: url(https://tmuracdn.blob.core.windows.net/club/itu/app/appgif.gif) , url(https://tmuracdn.blob.core.windows.net/club/itu/app/appbg.jpg);
    background-size: cover;
    background-repeat: no-repeat;
    background-size: 800px,500px;
    background-repeat: no-repeat;
    background-position: 510px 200px , 650px 10px;
    height: 900px;
    /* background-color: blue; */
}


#mainDiv *{ 
    display:none!important;
}