function show(id) {
   var element = document.getElementById("super" + id);
   var expand_mark = document.getElementById("expand_mark" + id );
   var expand_mark_value = expand_mark.innerHTML;
   var new_value = '';
   if ( element.style.display == "none" ) {
       element.style.display = "block";
       new_value = expand_mark_value.replace(/^\s*\+/,' -');
   }
   else {
       element.style.display = "none";
       new_value = expand_mark_value.replace(/^\s*-/,' +');
   }
   expand_mark.innerHTML = new_value;
       
}