function switch_dayMenu(curr_id, total_num) {    
 for(var i=0; i<total_num; i++)     {         
     var el = document.getElementById('daymenu_sub_'+i); 
     if(!el) return;        
     var img = document.getElementById('daymenu_master_'+i); 
     if(i == curr_id) {   
          el.style.display = "block"; 
          img.src = "images/day_number/day_nums"+i+"a.jpg"; 
      } else{            
          el.style.display = "none";
         img.src = "images/day_number/day_nums"+i+".jpg";
     } 
  } 
}