function closeAd() { 
	if(document.layers) { 
		document.layers['hf_ad'].visibility = "hide"; 
	} else if(document.getElementById) { 
		var obj = document.getElementById('hf_ad'); 
		obj.style.visibility = "hidden"; 
	} else if(document.all) { 
		document.all['hf_ad'].style.visibility = "hidden"; 
	} 
}