#overlay {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    height: 100%;
    display:table;
    background: rgba(0, 0, 0, 0.5);
    z-index: 99999;
}

#text{
    display:table-cell;
    vertical-align:middle;
    text-align:center;
}