Thanks for your quick response;
i disabled the cron then loged onto the site-> anabled cron again everything seems work ok. but i when i logout the site is blank. the cron may conflict with something on my landing page.
My question is : can I just insert the code "<?php /*JCron Code*/ $from_template = 1;@include('components/com_jcron/jcron.php'

;/*DO NOT REMOVE ANYTHING*/ ?>" into my index.php instead of clicking on "enable cron run" in back end? I mean to make cron running without enabling the cron in configuration?
if ok, i can control the cron not running on outside page. where is the best place to put the line code, in header, body or...?
Thanks for your response,
Kim.