var open_node = null;

function off_on(nid)
{
   var node = document.getElementById(nid);
   var def_node = document.getElementById('def');
   if(node.style.display == 'block'){
     node.style.display = (node.style.display == 'block') ? 'none' : 'block';
     def_node.style.display = 'block';
     open_node = null;
   }else{
     if(open_node) open_node.style.display = 'none';
     node.style.display = 'block';
     def_node.style.display = 'none';
     open_node = node;
   }

}