Where can I find apache error_log on CentOS
Solution 1:
Check your httpd.conf
The LogFile variable tells you where apache is writing logs. This value is often (always?) relative to the ServerRoot variable.
Solution 2:
Chances are it's in /var/log/httpd.
Do you have locate installed? Have you run updatedb recently, or have it cronified? If so, you can do locate error_log.
Solution 3:
take a look at your /etc/httpd.conf file and check where you are writing your logs valter. as Raffael says it maybe that you've got them being written to odd locations. check that your httpd server actually started too! :-)