The injunction to separate content from presentation is idealistic at best.
The very concept of content is misleading. Talking about content, communication gurus refer to text. But text is not content. Content alludes to some kind of objective meaning, which can be thought outside this world, or inside the head, like some kind of mentalese. In any case, the very idea of content is problematic, from a philosophical point of view.
A content management system is mostly a shovelware, an assistant that shovels texts from a media (e.g. notebook) to another (e.g. internet). What is kept under control is not the presentation, nor the texts, but the very idea of controlling anything right from the start. Presentation, in this context, entails all the structure, including the navigation system.
A CMS helps writing because writing suffices to get going. But that does not get us very far : it lasts for a while, until the load of texts bend and break the first structural choices. Tweaking the structure entails having a second look at the texts as a whole.
Texts depends on their presentation to work, and their presentation details depend on the texts. So presentation and content are co-dependencies. They should be separated, but kept very close one to another.
