function toggle_submenu( name )
{
  var links = document.getElementsByTagName("a");
  
  for( var i = 0; i < links.length; i++ )
  {
    if( links[i].id.substr(0, name.length) == name && links[i].id.length > name.length )
    {
      if( links[i].parentNode.style.display == 'none' )
      {
        links[i].parentNode.style.display = 'block';
        document.getElementById( name + '_icon' ).src = '/images/menudrop.png';
      }
      else
      {
        links[i].parentNode.style.display = 'none';
        document.getElementById( name + '_icon' ).src = '/images/menudrop.png';
      }
    }
  }
}

function toggle_et()
{
  toggle_submenu('menu_et');
}

function toggle_bul()
{
  toggle_submenu('menu_bul');
}

function toggle_bc()
{
  toggle_submenu('menu_bc');
}