function nav_in( element, is_active)
  {
  if( is_active )
    document.getElementById( element ).src = '/img/navi/'+element+'_hi.gif';
  else
    document.getElementById( element ).src = '/img/navi/'+element+'_ro.gif';
  }
function nav_out( element, is_active )
  {
  if( is_active )
    document.getElementById( element ).src = '/img/navi/'+element+'_hi.gif';
  else
    document.getElementById( element ).src = '/img/navi/'+element+'.gif';
  }

function nav2_in( element, is_active)
  {
  if( is_active )
    document.getElementById( element ).src = '/img/subnavi/'+element+'_hi.gif';
  else
    document.getElementById( element ).src = '/img/subnavi/'+element+'_ro.gif';
  }
function nav2_out( element, is_active )
  {
  if( is_active )
    document.getElementById( element ).src = '/img/subnavi/'+element+'_hi.gif';
  else
    document.getElementById( element ).src = '/img/subnavi/'+element+'.gif';
  }