effects blocking a user from the user page:

if you block a user from his/her profile page

• the blocked user will not be able to see your profile page anymore
• the blocked user will not be able to see your pictures anymore
• the blocked user will not be able to see your favorites or your profile completion page anymore
• the blocked user will not be able to write to you anymore
• the blocked user will not be able to send you instant messages anymore
• the blocked user will not see you in the search results anymore
• you will not see the blocked user in the search results anymore
• the blocked user will appear in your list of blocked users and you can go there to unblock the user at any time

effects blocking a user from the messages inbox:

you can also block a user only from sending you messages from your messages inbox, doing this will cause messages sent by this user to go in the junk and you will not receive any email notification when this user sends you a message if you have selected this option. also emails sent by blocked senders will not count as new messages

effects blocking a guest from the instant message window:

when you block a guest in this manner (and guests can also themselves block other guests) it places a rule in the database for 7 days that prevents the blocked guest or any other guest with the same ip address to send you instant messages for that period of time. you can unblock a guest before the 7 days expiration from your list of blocked users