Thank you Solo Honk,

Regarding png.php
Line 21,
define('JPATH_BASE', $_SERVER['DOCUMENT_ROOT'] );
to
define( 'JPATH_BASE', realpath(dirname(__FILE__).'/../../..' ));

is this all you changed?
I have tried this but still have problem.

I do not know which path should I get ....

That's exactly what I've changed in png.php.
Maybe you must clear your browser cache.

Thank you, SoloHonk.
I still have the problem....

I've installed Joomla! to my sub-directory.
When I check the source code on my site(frontpage), I see the wrong path to get the background-image like this....

<style type="text/css">#pcdtr**{background-image:url(/SUB_FOLDER_NAMEplugins/system/pcdtr/png.php?id=*&rand=*);width:**px;height:**px;}</style>

I think it should be like this....
<style type="text/css">#pcdtr**{background-image:url(/SUB_FOLDER_NAME/plugins/system/pcdtr/png.php?id=*&rand=*);width:**px;height:**px;}</style>

If you download and install the latest 1.9.9 it fix both problems.

flowman wrote:
If you download and install the latest 1.9.9 it fix both problems.

Works Perfect!
Thanks!