function OpenMenu(id){ 
			document.getElementById( id ).style.visibility = 'visible';
		}
		function CloseMenu(id){ 
			document.getElementById( id ).style.visibility = 'hidden';
		}
		
if (document.images) {
   img1 = new Image(); img1.src = "img/bt_top_01_b.jpg";
   img2 = new Image(); img2.src = "img/bt_top_02_b.jpg";  
   img3 = new Image(); img3.src = "img/bt_top_03_b.jpg";  
   img4 = new Image(); img4.src = "img/bt_top_04_b.jpg";  
   img5 = new Image(); img5.src = "img/bt_top_05_b.jpg"; 
   img6 = new Image(); img6.src = "img/bt_01_b.jpg"; 
   img7 = new Image(); img7.src = "img/bt_02_b.jpg"; 
   img8 = new Image(); img8.src = "img/bt_03_b.jpg"; 
   img9 = new Image(); img9.src = "img/bt_04_b.jpg"; 
   img10 = new Image(); img10.src = "img/bt_05_b.jpg"; 
   img11 = new Image(); img11.src = "img/bt_06_b.jpg"; 
   img12 = new Image(); img12.src = "img/bt_07_b.jpg"; 
   img13 = new Image(); img13.src = "img/bt_08_b.jpg"; 
   img14 = new Image(); img14.src = "img/bt_09_b.jpg"; 
   img15 = new Image(); img15.src = "img/bt_top_07_b.jpg"; 
  
}
function setImage(img, image) {
   if (img) {
      img.src = image;
   }
}