Download and install Sigil. Open the epub with Sigil, locate the content.opf file at the bottom of the file browser window and open it. Browse down to line 51.
At a WEG, you'll see a line similar to the following:
Code:
<reference type="text" title="Dedication" href="Text/part003.xhtml#aid-39"/>
where the #aid-39 is a fragment identifier which should match to an id="aid-39" somewhere in one of the text files. For the most part, you can remove the identifier since it has already been removed elsewhere.
You might want to take a look at
ePub Error fragment identifier is not defined in OEBPS for more information.
Edit: Please do not double post. It's extremely annoying to read multiple posts with the same content.