Ti ringrazio veramente Vindav!

solo che non mi funziona...
Dove sbaglio???

codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Documento senza titolo</title>

<script>
function deselectAll(){
	var myradio = document.getElementsByClassName('radio');
	for(i=0;i<myradio.length;i++) radio.item(i).checked = false;
}

</script>
</head>

<body>

[img]img/inserisci.gif[/img]

<form >
<input type="radio" value="1" name="frase" class="radio"  />
<input type="radio" value="2" name="frase" class="radio"  />
<input type="radio" value="3" name="frase" class="radio"  />
<input type="radio" value="4" name="frase" class="radio"  />
</form>

</body>
</html>