#divFormLogin {
    position: absolute;
    left: 50%;
    top: 40%;
    margin-top: -195px;
    margin-left: -160px;
    width: 320px;
    padding: 20px;
    border-radius: 10px;
}

#overlay{
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 10;
    background-color: rgba(0,0,0,0.5); /*dim the background*/    
}