function show_block(id){
      var art='block';
      if(show_block.arguments.length>1)
      art=show_block.arguments[1];
      var e = document.getElementById(id);
      if(e.style.display != art)
         e.style.display=art;
      else
         e.style.display='none';
      }
      function hide_block(id){
      var e = document.getElementById(id);
      e.style.display='none';
      }