I've built a few tailor-made Content Management Systems for websites in the past, and one thing I've realised is that it's impossible to control the way the CMS user inputs content. Most simply cut and paste from Word, which makes awful, untidy, invalid code, and on top of that, they're likely to forget that you need to write concisely (in order to maintain attention). Accessibility is most likely out of the question unless they get plenty of training and theory explaining its importance.

There are several tools you can use to simulate a word-processor within a web browser, but they're often supported by one browser and generate poor quality code.

The best tool I've found for this purpose is TinyMCE. It's a powerful application that can be customised easily when setting up. It's the editor used by Wordpress, and with some work, it will generate valid XHTML code. It also has a plugin architecture with many great plugins to do various tasks.

I recently read an article on 456bereastreet.com that touched this subject and talked about the What You See Is What You Mean (WYSIWYM) editor. A good article that I'd recommend reading if you're involved with CMS's or with blogs. The way its different from WYSIWYG is that its intention is to concentrate on "the structure and meaning" rather than the visual aspects.

I reckon that when users start to get serious about following the disability guidelines, this editor will explode in popularity. It already provides a strong basis for all other editors out there, as it concentrates on what will become the most important aspects of websites - semantics, usability and accessibility.

I'm going to keep a close eye on its developments.