You erase it and pretend you know nothing of it.
You make him/her listen to it and then you demand an explanation
You suggest bringing his/her ex over for a dinner
You let him/her go and seek your own fun.
You watch it in order to see where it leads to
You make a scene
You ask for a reason and check his/her text messages to see where he/she is going and whom with
You spill something on him/her pretending it was accidental.
You think he/she is gorgeous and you compliment him/her.
You use the opportunity when no one's watching to step on his/her foot
You stand in between
You're glad that other people are attracted to your partner as well.
You demand to leave the cinema immediately.
You say how that actor/actress must have had few plastic surgeries
You are entertained by his/her reaction and you tell him/her about your favorite actor/actress
You log in as soon as possible and check out his inbox/outbox/etc...
You save it in your phone. Knowing it can't do any damage.
You don't care about it.