[CentOS] file permissions and groups

> All permissions are 755 owned by root:root up to /var/www/html and then
> /var/www/html/subdir is owned by apache:apache with mode 755.
>
> Unfortunately, there is nothing useful in the apache logs, either.

Do you have SELinux enabled?  Does your file have the correct context 
owner?  Do you have any ACLs enabled?