Better yet for the FCK.xml file:
The example above has element="span" for such custom styles as Title and Topic. The trouble with that approach is that the style won't get applied to the paragraph tag, but with a set of span tags.
Since the editor natively puts <p> tags around each paragraph or block of copy, set element="p" instead. In that way, the paragraph tag itself gets the style attribute and makes for much cleaner code. In addition, the styles can be changed much easier if experimenting with several different styles when applying to a paragraph.