function change_state (f)
{
if (document.getElementById(f).style.display=='none')
  {
    document.getElementById(f).style.display='block';
    if (document.getElementById(f+"_a").className=='') document.getElementById(f+"_a").className="activ_m";
    if (document.getElementById(f+"_a").className=='bold_s') document.getElementById(f+"_a").className="bold_s activ_m";
  }
  else
  {
    document.getElementById(f).style.display='none';
    if (document.getElementById(f+"_a").className=='activ_m') document.getElementById(f+"_a").className="";
    if (document.getElementById(f+"_a").className=='bold_s activ_m') document.getElementById(f+"_a").className="bold_s";

  }
  return false;
}