.modalPopup {
    position: fixed; /* stays relative to browser window */
    top: 0; /* distance from top */
    left: 0; /* distance from left */
    background-color: #fff;
    border: 2px solid #666;
    padding: 20px;
    width: 250px;
}

.modalBackground {
    background-color: rgba(0,0,0,0.5);
}