function change_description(id_zone){
        
        document.getElementById('haut_description_zones').style.display = "block";
        
        document.getElementById('bas_description_zones').style.display = "block";
        
        var tabDivs = document.getElementById('milieu_description_zones').getElementsByTagName('div');
        
        var longueur = tabDivs.length;
        
        for (var i = 0; i < longueur; i++) {
            
              tabDivs[i].style.display = "none";  
            
        }
        
        document.getElementById('desczone'+id_zone).style.display = "block";
        
}