#footer a.lien-univ {
    background-image: url('https://ose.univ-lyon1.fr/images/logo.png');
    background-repeat: no-repeat;
    background-position: right top;
    background-size: contain;
    display: ruby-text;
    height: 50px;
    width: 50px;
    text-indent: -9999px;