var ns = false;                                                
		var browser = navigator.userAgent.substring(0,9);      
		if (browser == "Mozilla/3" || browser == "Mozilla/4") ns = true;

		var dot_normal , dot_hot;
		if (ns){
		   dot_normal = new Image (42,10);
		   dot_normal.src = "image/dot_off.gif";
		  
		   dot_hot = new Image (42,10);
		   dot_hot.src = "image/dot_on.gif";
		}

		function switchimage (imagename, target)
		{
		   if (ns) document.images[imagename].src = target.src;
		}