When you delete a forum all its topics and replies will be deleted too. You will see a notice about the number of topics and replies in the forum and should confirm the deletion.
Metainfo:
Author: Webservices GmbH factline; Copyright: factline Webservices GmbH; Published by: Webservices factline 4 (factline4) factID: 1315355.5 (...history); published on 11 Jan. 2010 13:23
