You must check httpd.conf
you can check by " httpd -S"
You must check /var/log/messages and read eroor for apache why dont start.
Running `service httpd configtest` will check you current configuration and report on errors
found. It might point you in the right direction. Also check the logs in /var/log/httpd.
Do you know if apache was upgraded from 1.3.x to 2.x.x . Could be you have installed a later
version but still have old confs.
I'd guess that there's more logging information needed from error.log,