403 Forbidden error Wordpress Plugin

Hi,

I Installed one plugin on my website "http://www.hootex.com/wp-content/plugins/Share-This-Image/sharer.php"

It's giving "403 Forbidden" error while running.

plugin developer saying it's a file/directory permission issue.

I have set the permissions to 777 for every file and directory of this plugin but the problem not solved.

I see there is USER and GROUP in my plesk file manager. my USER is hootex and GROUP is psacln

(Please find attached photo)

I have read somewhere...

403 Forbidden error Wordpress Plugin