I run a free hosting company, and I'd like to start putting an ad code at the bottom of each page served on accounts. Is there anyway to do this by modifying the templates in /var/cpanel/templates/apache2/?

Thanks for your help in advance.

The only effective way of accomplishing what you're describing is to use mod_layout. mod_rewrite rules don't work 100% of the time and modifying any sort of cPanel template or skeleton directory files won't do the trick either.

May be it would be better if you look for a "free hosting" panels. They have been made for that purpose.