What is the duty or standard of care owed by an invitor to an invitee?

The plaintiff was an invitee, and the duty or standard of care owed by an invitor to an invitee is set out in Indemaur v. Dames, (1866] L.R. 1 C.P. 274: And, with respect to such a visitor at least, we consider it settled law, that he, using reasonable care on his part for his own safety, is entitled to expect that the occupier shall on his part use reasonable care to prevent damage from unusual danger, which he knows or ought to know; and that, where there is evidence of neglect, the question whether such reasonable care has been taken, by notice, lighting, guarding or otherwise, and whether there was contributory negligence in the sufferer, must be determined as a question of fact.