When a Facebook contact no longer wishes to communicate with you via the site, he blocks you, which prevents the two of you from seeing one another's profiles or sending messages to one another. If you believe someone has blocked you accidentally or due to erroneous information, contact him off the site and ask him politely to unblock you. Do not create a fictitious Facebook identity and attempt to win him over that way.
Send your contact a message via email and tell him you don't understand his reasons for having blocked you. Ask him to explain himself or, if the blocking occurred in error, to unblock you at once.
Call your contact if you know him personally. Explain to him that you have been blocked from his profile and request that he remove the block.
Avoid desperate tactics, such as creating alternate Facebook identities or involving mutual friends in the conflict. If a friend has blocked you and he didn't do so accidentally, respect his decision, at least for the time being. The friend may realize he was wrong in the future and unblock you as an apology.