/* Set initial hidden state and smooth transition */
#my-div {
    opacity: 0;
    transition: opacity 2s ease-in-out; /* Takes 2 seconds to fade in completely */

    position: absolute;
    top: 256px;
    left: 600px;
}

/* Class added by JavaScript to trigger the fade */
#my-div.visible {
    opacity: 1;
}