function toggleVisible(id) {
  var item = document.getElementById(id);
  var value = item.style.display ? '' : 'none';
  item.style.display = value;
}

function switchButton(id) {
  var item = document.getElementById(id);
  if (item.src.search(/plus/) != -1)
	item.src = item.src.replace(/plus/,'minus');
  else if (item.src.search(/minus/) != -1)
	item.src = item.src.replace(/minus/,'plus');
}