apache error logs

[peman]

Hello,

Today our apache stopped working for some reason. i restarted the services and now it works. where are the ordinary apache error log file? mine is empty under /var/log/apache2/error.log, has ispCP an error log of its own? or where can find what happened to apache?

Also i need to know if there is some kind of program like Nagios or something better that can notice me if apache is down?