I am sure a lot of you are aware of WYSIWYG. Most of the editors where you can select the font, the style and the colors are WYSIWYG editors, where the underlying markup is hidden under these GUI controls for formatting. I got introduced to What You See Is What You Mean (WYSIWYM) through Peter Krantz. The difference can be expressed in one word – semantics – but makes a world of difference!
This is one of the reasons I do not like to use WYSIWYG editors, whether online or offline, I use the ones where markup can be typed, either directly or through text generators like Markdown or Textile. I do not want to work on formatting while writing, I want to work on semantics. Formatting will be handled by stylesheets. Peter mentions WYMEditor, that is intended to be an editor that stresses on meanings rather than formattings. This should help a lot. Like Peter says CMSs should lookout for it. And I will too!