function showdiv (targetdiv) {
  document.getElementById('vents').style.visibility='hidden';
  document.getElementById('exteriorsiding').style.visibility='hidden';
  document.getElementById('eaves').style.visibility='hidden';
  document.getElementById('chimney').style.visibility='hidden';
  document.getElementById('raingutter').style.visibility='hidden';
  document.getElementById('roof').style.visibility='hidden';
  document.getElementById('firewood').style.visibility='hidden';
  document.getElementById('flammableitems').style.visibility='hidden';
  document.getElementById('windows').style.visibility='hidden';
  document.getElementById('decks').style.visibility='hidden';
  if (targetdiv) {
    document.getElementById(targetdiv).style.visibility='visible';
  }
}