if(document.images){

		_srv_on=new Image();
		_srv_on.src="images/nav_srv_l.gif";
		
		_srv_off=new Image();
		_srv_off.src="images/nav_srv.gif";

		_air_on=new Image();
		_air_on.src="images/nav_air_l.gif";
		
		_air_off=new Image();
		_air_off.src="images/nav_air.gif";		
		
		_res_on=new Image();
		_res_on.src="images/nav_res_l.gif";
		
		_res_off=new Image();
		_res_off.src="images/nav_res.gif";		

		_car_on=new Image();
		_car_on.src="images/nav_car_l.gif";
		
		_car_off=new Image();
		_car_off.src="images/nav_car.gif";		

		_con_on=new Image();
		_con_on.src="images/nav_con_l.gif";
		
		_con_off=new Image();
		_con_off.src="images/nav_con.gif";		
		}
		
		function img_act(imgName) {
		             {
					 if (document.images) { 
		             imgOn = eval(imgName + "on.src");
		             document [imgName].src = imgOn;}
		             }
		     }
		
		function img_inact(imgName) {
		             {
					if (document.images) { 
		             imgOff = eval(imgName + "off.src");
		             document [imgName].src = imgOff;}
		             }
		    }