up0 = new Image(); 
  up0.src = "a_netw.gif"; 
  down0 = new Image(); 
  down0.src = "a_netw0.gif";
  
  up1 = new Image(); 
  up1.src = "a_prog.gif"; 
  down1 = new Image(); 
  down1.src = "a_prog0.gif";
  
  up2 = new Image(); 
  up2.src = "a_syst.gif"; 
  down2 = new Image(); 
  down2.src = "a_syst0.gif";
  
  up3 = new Image(); 
  up3.src = "a_refe.gif"; 
  down3 = new Image(); 
  down3.src = "a_refe0.gif";
  
  up4 = new Image(); 
  up4.src = "a_cont.gif"; 
  down4 = new Image(); 
  down4.src = "a_cont0.gif";
  
  up5 = new Image(); 
  up5.src = "a_prod.gif"; 
  down5 = new Image(); 
  down5.src = "a_prod0.gif";

  up6 = new Image(); 
  up6.src = "a_down.gif"; 
  down6 = new Image(); 
  down6.src = "a_down0.gif";
    
  up7 = new Image(); 
  up7.src = "a_link.gif"; 
  down7 = new Image(); 
  down7.src = "a_link0.gif";
  
  up8 = new Image(); 
  up8.src = "a_home.gif"; 
  down8 = new Image(); 
  down8.src = "a_home0.gif";


  function bw( nr, object ) {
  	window.document.images[nr].src = object.src;
  }