[jQuery] Error with custom method

[jQuery] Error with custom method


Hi,
I try to make a custom method which indicates if the field "room
Number" is available. And I have this error :
jQuery.validator.methods[method] is undefined
with this code :
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/
TR/html4/strict.dtd">
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html;
charset=iso-8859-1" />
        <title>Untitled Document</title>
        <link href="style/cmxformTemplate.css" type="text/css"
rel="stylesheet" />
        <script type="text/javascript" src="javascript/
jquery-1.2.6.min.js"></script>
<script type="text/javascript" src="javascript/
jquery.validate.min.js"></script>
    </head>
    <body>
        <form id="conferenceForm" class="cmxform"
action="javascript:alert('OK');" method="post" autocomplete="off">
    <fieldset>
        


            <label for="jqmRoomNumber">Room Number</label>
            <em>*</em>
            <input type="text" MAXLENGTH="6" id="jqmRoomNumber"
name="jqmRoomNumber"/>
        





        


            <input type="submit" value="Create"/>
            <input type="button" value="Cancel" onclick="hidePopup()" />
        



    </fieldset>
</form>
<script type="text/javascript">
    $(function() {
        $.validator.addMethod("roomNumber", function (value, element, param)
{
            return true;
        },
        "Your room number is not available");
        $("#conferenceForm").validate({
            rules: {
                jqmRoomNumber: {
                    required: true,
                    roomNumber:true,
                    minLength:2
                }
            },
            messages: {
                jqmRoomNumber: {
                    required: "Please enter a room Number",
                    minLength: "Your login must consist of at least 2 characters"
                }
            }
        });
    });
</script>
    </body>
</html>
For now, I have made un simple custom method which return always
"true" to understand how .