.screenUnlocked
{
    display: none;
    visibility: hidden;
}

.screenLocked {
    display: table;
    visibility: visible;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: #ccc;
    text-align: center;
    filter: alpha(opacity=85);
    opacity: 0.85;
    z-index: 2147483647;
}

#screenLock > span {
    display: table-cell;
    vertical-align: middle;
}