Firstly I'm sorry that the answer I'm sure should be a simple one, I'm just seeming to be spending a long time not yet finding the simple answer, or how to implement my ideas!

I currently have the choice of 3 CMS systems ready to run on my host server for clients:
- Joomla CMS 1.5
- Mambo CMS
- Drupal CMS

Plus I have WordPress Blog, and I can configure Blogger templates quite easily to be hosted on their domain (although I'd prefer not to have to build new sites as a blog).

I'm competent with html and CSS, and always try to minimise excess coding in all my pages as much as possible, keeping them SEO, cross platform, accessible, W3C, ...

I've taught some of my clients basic html, so they can make simple edits to their existing websites via their online file manager (who generally come back to me with bigger updates as and when).
However, I'm now trying to move into being able to utilise a suitable online based CMS, so that clients can make suitable edits for themselves, by a number of users, adding new pages, editing content, external links, etc. (ie so they can edit much in the same way as a word document, or WYSIWYG, without needing to go into the source code directly, but giving the options for me to do this as and when). So essentially setting up a clean html template, with editable regions, and standard selections of style markers (ie h1, h2, p, img, etc.)

I'm keen to keep the files with unique html pages across the site (rather than PHP type database driven content of a single page, within index.php?option=....)

So can anyone point me in the right direction, of where to set up the html and external CSS, etc., so that my clients can use one of the above CMS to manage their content, whilst still keeping it as pure html as possible and a usual tree based directory structure?

There must be an easy(ish) answer with at least one of those CMS systems?