function preload()
  {
    top_logo_1 = new Image();
    top_logo_1.src = '../images/header1.jpg';

    top_logo_2 = new Image();
    top_logo_2.src = '../images/header2.jpg';    
	
    top_logo_3 = new Image();
    top_logo_3.src = '../images/header3.jpg';    
	
    top_logo_bg = new Image();
    top_logo_bg.src = '../images/header_bg.jpg';    
	
    nav_bg = new Image();
    nav_bg.src = '../images/nav_bg.jpg';    
  }