.subscribe-popup {
    display: none;
    position: fixed;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.7);
    z-index: 1000;
    padding-top: 100px;
}

.close-popup {
    color: #aaa;
    position: absolute;  /* Make it absolute */
    top: 10px;           /* Position from the top */
    right: 10px;         /* Position from the right */
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
}

.close-popup:hover,
.close-popup:focus {
    color: #000;
    text-decoration: none;
    cursor: pointer;
}