nbMenus = 3

function MontrerMenu(strMenu)
{
    CacherMenus();  
    document.getElementById(strMenu).style.visibility="visible";
}

function CacherMenus()
{
    for(i=1;i<=nbMenus;i++) {
      with(document.getElementById("menu"+i).style) {
        visibility="hidden";
      }
    }
}