> a.      hyperlinks referring to a page within the web 
site 
> to which that page,belongs (navigational or context)

Generally internal (caught) pages

> b.      outbound links

"External" links for httrack

> I thought the outbound links could be 
> checked with the option 'Test,links in pages (bookmark 
> test)'

No! This option only checks the first-level links given in 
the first URL page ; that is, it only checks links (and do 
NOT follow them)

> I already checked the box 'Test validity of all links 
(even 
> external
> ones) on the Option-Links tag. In addition I chose 
the 'Go 
> everywhere on the web' option from the Global Travel mode 

Wow - do not touch the expert settings ; filters are more 
powerful and potentially less dangerous.

If you want to check external links in a website, I would:
- make a regular mirror ("Mirror website")
- erase all default filters in Options/Scan rules
- activate "test validity of all links"

HTTrack will then mirror tour site, and test external 
links. If an error (404, ..) is encountered, it will be 
logged in hts-log.txt