Well you have the permutations,
(email, Facebook, porn)
(email, porn, Facebook)
(porn, email, Facebook)
(Facebook, email, porn)
(Facebook, porn, email)
(porn, Facebook, email)
That is 3! or 6 total possibilities, 2 of which involved porn immediately following Facebook. which is 1 in 3... ...How do you figure 1 in 2?