codice:
<!doctype html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Pagina vuota</title>
<script type="text/javascript">
function countSubmit() {
	var oBtn = document.myForm.mySubmit, nTime = parseFloat(/\d+/.exec(oBtn.value)) - 1;
	if (nTime < 1) { clearInterval(nInterv); oBtn.value = "Invia!"; oBtn.disabled = false; return; }
	oBtn.value = oBtn.value.replace(/\d+/, String(nTime));
}
var nInterv = setInterval(countSubmit, 1000);
</script>
</head>

<body>
<form name="myForm">
<input type="submit" disabled="true" name="mySubmit" value="mancano 6 secondi" />
</form>
</body>
</html>