I've found the really great editor which is different from FCKEditor and maybe easier to handle for users, without any knowlege of html. FCK is working well, but I often see how users re- and deformat their content because they don't know what they do inside FCKEditor.
http://www.wymeditor.org/en/Why WYMeditor ?
Do you modify your website using a content management system (CMS)? Do you allow your clients to modify their website whith a CMS?
If yes, you have certainly met de difficult choice of a web-based (x)html editor.
* You may have tried FCKeditor, or HTMLarea, but you apprehend that your clients use it unappropriately, with the risk it degenerates visually and on the code quality.
* You may also have tried the BBcode syntax, Markdown or the wiki-style syntax, but you don't want to force your clients to solutions that are too technical/complex for them, even if it tends to generate good quality code.
WYMeditor brings a new approach and a set of simple solutions which allow for a very easy to use editor, while still producing clean XHTML code. Thanks to its original approach it remains clear and easy to learn. A one-hour training and it's the beginning of clean updates made by the end user.
best, marcus