Webcomic is a plugin for the WordPress publishing platform, so the most important requirement is a functioning installation of WordPress or WordPress MU.

PHP 5

Unlike WordPress, Webcomic requires at least PHP 5. Most hosts provide and default to PHP 5, but if you’re not sure you may want to ask your host before installing Webcomic.

Directory Permissions

For maximum ease-of-use Webcomic also needs permission to create directories in your WordPress directory. Most of the time you won't need to mess with directory permissions, but Webcomic will notify you if it is unable to automatically generate necessary directories for you which often means a directory permissions problem.