There are many reasons someone might block you on Facebook.
Maybe you broke their heart and it's too painful for them to see pictures of you, or you've had a falling out and they don't want to associate with you any more.
Or maybe you're just a general pain in the arse.
Either way, there's a way to find out if you've been given the digital cold shoulder.
First of all, try searching for that person's name on Facebook.
If nothing comes up, that's often a bad sign, but ask a mutual friend to check if they can find them.
If they can, the person hasn't just deleted their account - you've been blacklisted.
You now won't be able to view that person's profile, send them a message, or see any of their comments on Facebook.