function hideLayer(whichLayer) {
        if (document.getElementById) { // standard
             document.getElementById(whichLayer).style.visibility = "hidden";
        }
        else if (document.all) {// old msie
             document.all[whichlayer].style.visibility = "hidden";
        }
        else if (document.layers) {// nn4
             document.layers[whichLayer].visibility = "hidden";
        }
}

function showLayer(whichLayer) {
        if (document.getElementById) { // standard
             document.getElementById(whichLayer).style.visibility = "visible";
        }
        else if (document.all) { // old msie
             document.all[whichlayer].style.visibility = "visible";
        }
        else if (document.layers) { // nn4
             document.layers[whichLayer].visibility = "visible";
        }
}