codice:
<html>
<head>
<script langauge="javascript">

function show_hide(c) {
  document.getElementById(c.name+"field").style.display = (document.getElementById(c.name+"field").style.display=="none" ? "inline" : 

"none");
  c.style.color = (c.style.color == "red" ? "black" : "red");
}

</script>
<body>
<input type="button" value="*" name="commento_nome" onClick = "show_hide(this);">
<div id="commento_nomefield" style="display: none;">
  Commento Nome:<input type="text" value="inserisci commento"
</div>
</body>
</html>