For each site, Apache writes access and error information to log files. Each site has two log files - access_log and error_log, which store information on access to that site and errors respectively. Apache log files for each site are located in the /statistics/logs subdirectory of the virtual host directory /var/www/vhosts/<domain_name>, where domain_name is the name of a corresponding domain.
To save disk space, Panel rotates Apache logs. Learn how to change log rotation parameters in the Log rotation section.