var N4 = document.layers;
var IE = document.all;
var N6 = document.getElementById && !IE;

function display(layername) {
   if (N4){ document[layername].visibility = "show";}
   else if (IE){ document.all[layername].style.visibility = "visible";}
   else if (N6){ document.getElementById(layername).style.visibility = "visible";}
} 
function hide(layername) {
   if (N4){ document[layername].visibility = "hide";}
   else if (IE){ document.all[layername].style.visibility = "hidden";}
   else if (N6){ document.getElementById(layername).style.visibility = "hidden";}
}