Thanks Klaus for your reply. I try to put validate function into beforeSubmit section before i post in this group. I cannot force this validate function to return false when the field isn't filled up to cancel form submition.
Interesting thing is, that this particular validate function should return false, and should handle ajaxSubmit. I must missing something... some little bug :) I correct the "$(document).ready(function() " problem, and updated the sample page and zip file. So the problem isn't solved yet. Best regards, sławek