//preloading of images
	 button_on1 = new Image;
     button_on2 = new Image;
	 button_on3 = new Image;
     button_on4 = new Image;
	 button_on5 = new Image;
     button_on6 = new Image;
	 button_on7 = new Image;
     button_on8 = new Image;
	 button_on9 = new Image; 
	 
     button_on1.src = 'images/b1_on.gif';
     button_on2.src = 'images/b2_on.gif';
	 button_on3.src = 'images/b3_on.gif';
     button_on4.src = 'images/b4_on.gif';
	 button_on5.src = 'images/b5_on.gif';
     button_on6.src = 'images/b6_on.gif';
	 button_on7.src = 'images/b7_on.gif';
     button_on8.src = 'images/b8_on.gif';
	 button_on9.src = 'images/b9_on.gif'; 
	 
	function ChangeNavState(NavId,path){
		path = path; 
		document.getElementById(NavId).src= path;
		//alert (NavId+path);
		
	}
		
	function ChangeNavStateBack(NavId,name){ 
			document.getElementById(NavId).src= 'images/'+name+'_off.jpg';
			//alert (NavId+path);
	}