var isDOM = (document.getElementById ? true : false); 
var isIE4 = ((document.all && !isDOM) ? true : false);
var isNS4 = (document.layers ? true : false);


function getRef(id) {
    if (isDOM) return document.getElementById(id);
    if (isIE4) return document.all[id];
    if (isNS4) return document.layers[id];
}

function getSty(id) {
    return (isNS4 ? getRef(id) : getRef(id).style);
} 

function show(id){
  if(getRef(id))
		getSty(id).visibility = "visible";
}

function hide(id){
  if(getRef(id))
		getSty(id).visibility = "hidden";
}