Postings disappear here?

Why do I see only partial thread in a Newsgroups reader now, as some of the
postings get removed while entire trhead still appears at

??

We're missing several postings from Martha, then I go to
and there're all there but I can't respond to
Martha?
How is it possible?
How can a posting not be shown in Newsreader but appears on that website?
This means I can no longer trust Newsgroups but be forced in to Web
interface, I dont get it?