function fetch_object(idname)
{
 var my_obj = document.getElementById(idname);
 return my_obj;
}
function toggle_nav(obj)
{
 for (i = 1; i<= 6; i++ )
 {
  var sub_nav = fetch_object("sub_nav_" + i);
  var sub_nav_index = fetch_object("sub_nav_0");
  sub_nav_index.style.display = "none";
  if (obj == i)
  {
   sub_nav.style.display = "block";
  }
  else
  {
   sub_nav.style.display = "none";
  }
 }
}
function movepic(img_name,img_src) {
document[img_name].src=img_src;
}