ns4 = (document.layers) ? true:false; 
ie4 = (document.all) ? true:false; 
ng5 = (document.getElementById) ? true:false;

function hideAd(Ad) { 
	if (ng5) document.getElementById(Ad).style.visibility = 'hidden';
	else if (ns4) eval("document." + Ad + ".visibility = 'hide'");
	else if (ie4) eval(Ad + ".style.visibility = 'hidden'");
}

function showAd(Ad) { 
	if (ng5) document.getElementById(Ad).style.visibility = 'visible';
	else if (ns4) eval("document." + Ad + ".visibility = 'show'");
	else if (ie4) eval(Ad + ".style.visibility = 'visible'");
}