ok allora prova questo:


<script>
function sendform(idform)
{
if(document.getElementById(idform).text_name.value != "")
document.getElementById(idform).submit()
else
alert('vuoto')
}
</script>
<body >

<form id="id_form" name="form_name" action="javascript: alert('ho sottomesso il form')">
<input name="text_name" type="text" value="" onBlur="javascript:sendform('id_form')" >
</form>

dovrebbe essere la volta buona.....