is_ns4up = (document.layers)? true:false
is_ie4up = (document.all)? true:false
verOK = (is_ns4up || is_ie4up)

function affichage(id) {
        if (is_ns4up) document.layers[id].visibility = "show"
        else if (is_ie4up) document.all[id].style.visibility = "visible"
}

function effacement(id) {
        if (is_ns4up) document.layers[id].visibility = "hide"
        else if (is_ie4up) document.all[id].style.visibility = "hidden"
}

function rien()
{
}