TangoCMS
Description
TangoCMS is a PHP modular content management system released free of charge under the GNU/GPL 2 license. One of the top priorities for the project is to make sure that all mark-up complies to the World Wide Web Consortium XHTML standards, using semantically correct mark-up.
Like most content management systems, TangoCMS allows the owner/administrator of the website to create and manage content with no previous programming knowledge, including customizing the entire layout, user management and other administrative tasks.