How do i block someone on yahoo messenger & stop getting offline messages from that person?

To block senders in the downloaded Messenger program, go to Messenger > Preferences > Ignore List, and add the IM name or e-mail of the person you wish to block. Click Add, then OK or Apply. If you receive contact requests from unknown persons, go to the Ignore List and check 'Ignore anyone who is not on my contact list.' Then click OK or Apply. There appears to be no way to do this with the Mail version, especially with the fake 'Spam' chat messages, so you might want to download the program if you do not have it. Download and SAVE the program directly from the File Hippo web site. Download the most recent version of any Yahoo Instant Messenger (highest number, top of its list) Since Messenger 11 is still in beta format, you might prefer the earlier versions listed on the right of the page. You must be operating as an Administrator to install the program. Some firewalls have issues with installing Messenger from the Yahoo installer site, but disabling your firewall while online is VERY dangerous! Usually, by installing after downloading, the firewall will ask for permission to run the program. If you use Internet Explorer 8 or 9 as your browser, Yahoo Messenger 10 or 11 will not work properly without updated Flash and Java programs also installed, and possibly the .NET framework update.