la butto giù
codice:
<html>
<head>
<script>
  function submitForm(){
    if(document.getElementById("textfield").value.length==10)
       document.form1.submit();
  }
</script>
</head>
<body onload="document.form1.textfield.focus();">

<form name="form1" method="post" action="www.nuova_pagina.html">
<input type="text" name="textfield" id="textfield" onkeyup="submitForm();">
</form>

</body>
</html>
prova a vedere se va...