function on1() 
{if (!document.images) return; document.a.src = "/img/menu_01_a.gif";} 
function on2() 
{if (!document.images) return; document.b.src = "/img/menu_02_a.gif";}
function on3() 
{if (!document.images) return; document.c.src = "/img/menu_03_a.gif";}
function on4() 
{if (!document.images) return; document.d.src = "/img/menu_04_a.gif";}
function on5() 
{if (!document.images) return; document.e.src = "/img/menu_05_a.gif";}

function off1() 
{if (!document.images) return; document.a.src = "/img/menu_01.gif";}
function off2() 
{if (!document.images) return; document.b.src = "/img/menu_02.gif";}
function off3() 
{if (!document.images) return; document.c.src = "/img/menu_03.gif";}
function off4() 
{if (!document.images) return; document.d.src = "/img/menu_04.gif";}
function off5() 
{if (!document.images) return; document.e.src = "/img/menu_05.gif";}

var imgslist = new Array(
"/img/menu_01_a.gif",
"/img/menu_02_a.gif",
"/img/menu_03_a.gif",
"/img/menu_04_a.gif",
"/img/menu_05_a.gif"); 

var imgs=new Array(); 
for (x=0; x<imgslist.length; x++) 
 if (document.images) 
  {imgs[x]=new Image(); imgs[x].src = imgslist[x];}