function mapview(id,st) {
  img = getElement (id) ; if (! img) return ;
  ioff = getElement (id + "_off") ; if (! ioff) return ;
  ion = getElement (id + "_on") ; if (! ion) return ;
  if (st) {
    img.style.display = "block" ;
    ioff.style.display = "inline" ;
    ion.style.display = "none" ;
  } else {
    img.style.display = "none" ;
    ioff.style.display = "none" ;
    ion.style.display = "inline" ;
  } 
}