Either a technical glitch (a broken link) or the page has been taken down by the OP or Facebook,. The possible reasons for taking it down could fill volumes and still remain incomplete. Possibilities range from
  • “What was I thinking (or Why wasn’t I thinking?) when I posted that?
  • You mean everyone can see that, even my mother/partner/boss/spouse/the law!
  • The company is no longer in business.
  • “What do you mean, what i posted on Facebook can be copied down and used as evidence against me in a court of law? A political campaign? A loan application? An exposé?”
  • That is illegal material
  • The material is against Facebook policy
  • etc.

A broken link can and will be fixed (contact Facebook) a site that has been taken down contact your attorney or the OP.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein