function validateEmail(email) {
	   var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
	   return reg.test(email);
	}		

	function validateOnSubmit(){

		var emailF = document.getElementById("field_mail");

		if (emailF.value == "" || !validateEmail(emailF.value)){
			alert("Inserisci un indirizzo e-mail valido.");
			emailF.focus();
			return false;
		}				
		
		window.open('grazie.html','myWindow','width=482, height=239, top=270, left=380, toolbar=no, location=no, status=no, menubar=no, scrollbar=no, resizable=no');
		return true;
	}