function $(elementId){
    return document.getElementById(elementId);
}

function MenuOn(btn_name,elem){ 
var menuB=[]; 
   menuB[btn_name+elem]=new Image(); 
   menuB[btn_name+elem].src = 'img/'+btn_name+'_on.jpg'; 
   document.images['Men_'+btn_name+elem].src=menuB[btn_name+elem].src; 
   $(btn_name+elem).style.cursor = 'pointer'; 
} 

function MenuOff(btn_name,elem){ 
var menuA=[]; 
   menuA[btn_name+elem]=new Image(); 
   menuA[btn_name+elem].src = 'img/'+btn_name+'_off.jpg'; 
   document.images['Men_'+btn_name+elem].src=menuA[btn_name+elem].src; 
}