function afficher(id) {
    if (document.getElementById && document.getElementById(id) != null) {
        document.getElementById(id).style.visibility = 'visible';
        document.getElementById(id).style.display = 'block';
    }
}
function cacher(id) {
    if (document.getElementById && document.getElementById(id) != null) {
        document.getElementById(id).style.visibility = 'hidden';
        document.getElementById(id).style.display = 'none';
    }
}
function setBackground(id) {

    document.getElementById(id).style.backgroundImage = 'url(media/images/design/back_entete_main_menu.png)';
}
function removeBackground(id) {
    document.getElementById(id).style.backgroundImage = '';
}