<form action="" method="" name="formname"> <a href="#" onclick="window.open('privacy.html');return false;">leggi le condizioni</a> <input type="checkbox" name="checkboxname" value="ON" disabled="disabled"> accetta ... </form> ```in privacy.html metti:

<script language="JavaScript" type="text/javascript">
window.opener.formname.checkboxname.disabled=false;
</script>