CSS hacking for WYSIWYG CMSs
Chris Heilmann notes that many WYSIWYG CMSs that use in-page editing have problems with CSS based layouts in WYSIWYG CMS - The other user agent. He suggests setting up a repository of which CSS layouts break in what CMS to make it easier for developers to create editor stylesheets that will work around the problems.
It's certainly a good idea if you're working with a CMS that has an in-page WYSIWYG editing mode. Personally I would prefer disabling that feature (if possible) since I think it makes the content author focus more on layout than on content. But that isn't always doable, so making the best of the situation is a reasonable compromise.