#progress_bar {
    width: 100%;
    padding: 0px;
    display: none;
    background-color: #888;
    text-align: center;
    border-radius: 0px;
    /* (height of inner div) / 2 + padding */
    padding: 1px;
}

#progress_bar>div {
    background-color: #eee;
    width: 0%;
    /* Adjust with JavaScript */
    height: 8px;
    border-radius: 0px;
}