ciao, cosi`?

funzioncina:

function controlla() {
if (nomeForm.testo.value == "") {
alert("bla bla bla")
return false
}

return true
}



html:

<form name="nomeForm" onSubmit="return controlla()">
<input type="text" value="" name="testo">
<input type="submit">
</form>