Online WYSIWYG Editor

Recently I have had a problem with clients deleting/replacing web documents due to them trying to edit the pages themselves and being unfamiliar with ftp software.

I'm looking for an online WYSIWYG webpage editor. I'm looking for something I could implement into a control panel so that my clients don't take it upon themselves to use an ftp software and mess up scripts. I'm refering to just html documents. Documents with server side code are more complicated to edit. It would probably be best in that case to use external templates or something like that.

If anyone has ideas, references or knows of anything out there like I described I would appreciate the info.