Div Replace Sample

That's just a sample to provide an example about how you can use CKEditor, but you need to code the rest of the app by yourself. For example you would need to add some Id to identify what's being edited, think about what happens when a script is included in the content, or a flash movie...
The rest of the samples are also that way, they don't provide a full CMS, just a small code example to understand how to use it.