function is_mail_ok(mail)
{
	return (mail.match(/[A-Za-z0-9\._\-]+@[A-Za-z0-9\._\-]+\.[A-Za-z]{2,}/g) != null);
}

function add_comment(obj)
{
	var add_comment = obj.parentNode.nextSibling;
			
	while (add_comment.nodeType == 3)
		add_comment = add_comment.nextSibling;
	
	if (add_comment.className == "form_add_comment")
		add_comment.style.display = "block";
	
	return false;
}

function check_add_comment(formObj)
{
	if (formObj.name.value && formObj.email.value && formObj.comment.value)
	{
		if (is_mail_ok(formObj.email.value))
			return true;
		else
			alert("Zadaný e-mail je neplatný!");
	}
	else
		alert("Vyplňte všechny údaje!");
	
	return false;
}