What are validation errors in GeographyofBliss_oneChapter.epub?

If you have downloaded GeographyofBliss_oneChapter.epub from the adobe.com sample eBooks page, you may see validation errors with EpubCheck:

C:\fyicenter> java -jar epubcheck.jar GeographyofBliss_oneChapter.epub 

Validating using EPUB version 2.0.1 rules.

ERROR(NCX-001): GeographyofBliss_oneChapter.epub/OEBPS/GeographyofBli.ncx(-1,-1): 
  NCX identifier ("a9780446511070") does not match OPF identifier ("9780446511070").

ERROR(RSC-012): GeographyofBliss_oneChapter.epub/OEBPS/GeographyofBli.ncx(14,147): 
  Fragment identifier is not defined.

WARNING(OPF-003): GeographyofBliss_oneChapter.epub(-1,-1): 
  Item "OEBPS/images/Thumbs.db" exists in the EPUB, but is not declared in the OPF manifest.

WARNING(HTM-014): GeographyofBliss_oneChapter.epub/OEBPS/cover.xml(-1,-1): 
  Invalid file extension for HTML file, expecting (html, htm or xhtml).

As you can see from the output:

• GeographyofBliss_oneChapter.epub is EPUB 2.0 file.
• "ERROR(NCX-001)" message indicates that the NCX identifier in OEBPS/GeographyofBli.ncx does not match the OPF identifier in GeographyofBli_opf.opf.
• "ERROR(RSC-012)" message indicates that the fragment identifier is not defined at line # 14 in OEBPS/GeographyofBli.ncx.
• "WARNING(OPF-003)" message indicates that there is an extra file in the "./OEBPS/images" sub-directory: Thumbs.db. This is a simple database file created by operating systems to store thumbnails of picture files.
• "WARNING(HTM-014)" message indicates that a wrong file extension, *.xml, is used for an HTML file.

⇒ EPUB Tutorials

⇐ ERROR(NCX-001) - NCX identifier Not Match

⇑ Common Errors in Reported by EpubCheck

⇑⇑ EPUB Tutorials