On a Linux Server the default logging directory for Apache is /var/log/httpd (or /var/log/apache2 depending on your distribution) and the default Document root directory for the web files is /var/www/.
This means if everything is set up per default users shouldn't be able to access your error logs directly via http://url/etcetc quite simply because there's no log file there unless you're copying the log files over to the /var/www/ directory or if you've somehow included /var/log in your Document root directory in the apache configuration files.
Hope this provides an explination.