jQuery.validate.js how to add coustom message in form validation

<script src="jquery-1.6.2.min.js" type="text/javascript"></script>
<script src="jqueryui.js" type="text/javascript"></script>
<script src="jquery.validate.pack.js" type="text/javascript"></script>
<script type="text/javascript">
// validate form
 $("#myform").validate();

 // add new method specialChar to prevent special character in textfield
 jQuery.validator.addMethod("specialChar", function(value, element) {
   return this.optional(element) || /^[a-zA-Z0-9\s]+$/.test(value);
 }, "");

 // add coustom message

 jQuery.extend(jQuery.validator.messages, {
   required: "Error !", //message for required
   specialChar : "Special Character is not allow !", // message for special char
 });

</script>
<form id="myform" action="index.php" >
<input type="text" name="mydate" id="mydate" class="required specialChar"/>
<input type="submit" value="Submit" />
</form>
your code here