Foren / Cotonti / Support / SED_ABSOLUTE_URL

Using absolute urls is the only way to make adequate rewrite rules to create subdomains. And a system with a icluded rewriting method like Cotonti would consider this possibility...

Added 1 day later:

I think the core would control if the custom.function.php is enabled and if is passing absolute urls, or make a selectable feature in admin panel for webmasters using absolute urls in their rewriting methods...

Added 3 days later:

Sometimes I feel like asking useless questions to Cotonti Community...