Esempio veloce:
codice:
<head>
<script>
function verifica(){
var Psw = document.getElementById("password").value
var ConfPsw = document.getElementById("confermapassword").value
if(Psw!=ConfPsw){
alert("password e conferma discordanti");
return false;
}
}
</script>
</head>
<body>
<form name="MyForm" method="post" action="tuapagina.xxx">
<input type="password" name="password" id="password" />
<input type="password" name="confermapassword" id="confermapassword" />
<input name="Pulsante" type="button" value="Pulsante" onclick="verifica()" />
</form>
</body>