After movement of your s9y blog website to another place

mv /home/webmaster/public_html/blog.hostname.sk/ /home/webmaster/public_html/blog-s9y.hostname.sk/

you need to change serendipityPath path in s9y configuration, which is stored in your database:

SELECT * FROM `sp_config` WHERE `name` = 'serendipityPath' ;
UPDATE `sp_config` SET `value` = '/home/webmaster/public_html/blog-s9y.hostname.sk/' WHERE `name` = 'serendipityPath' ;