Note that the standard XHTML MES is configured for editing div's, table cells and list items. Editing of other elements (e.g. p, h1, inline elements) can be attempted but the code to correctly handle these is incomplete.
Here is the basic XHTML markup for the boxes below:
<div> <p>Edit <b>this bold section</b> of text!</p> </div>
<div>
editable via inline styleEdit this bold section of text!
<p>
editable via inline styleEdit this bold section of text!
<b>
editable via inline styleEdit this bold section of text!