$.getScript("js/jquery.form.js", function() {
    var options = { 
        target: '#main',   // target element(s) to be updated with server response 
		beforeSubmit: validate
    };
	
    function validate(formData, jqForm, options) { 
      var nameValue = $('input[@name=nome]').fieldValue(); 
      var emailValue = $('input[@name=email]').fieldValue();
	  var msgValue = $('textarea[@name=testo]').fieldValue();
   
      if (!nameValue[0] || !nameValue[0] || !msgValue[0]) { 
        alert('Devi compilare tutti i campi'); 
        return false; 
      } 
	}
	
    $('#formOne').ajaxForm(options); 
});