function showHideLayers(layer_name) {
	var objRows = document.getElementsByName(layer_name);
	for (i = 0; i < objRows.length; i++) {
  	if (objRows[i].style.display == 'none')
  		objRows[i].style.display = 'inline';
  	else
  		objRows[i].style.display = 'none';
  }
}