function navigueSousNav(num) {
    var menu = document.getElementById("elt"+num);
    var contenu = document.getElementById("sousNavContent"+num);
    menu.style.fontWeight="bold";
    for(var i=1; i<=5; i++) {
        if(i!=num) document.getElementById("elt"+i).style.fontWeight="normal";
    }
    contenu.style.display = "block";
    for(var j=1; j<=5; j++) {
        if(j!=num) document.getElementById("sousNavContent"+j).style.display="none";
    }
}