Sometimes you may need to block annoying IDs in yahoo messenger.You can follow the following path: Instant message box of any ID>conversation>preferences>ignore list>add>ok
Yes, it is so simple to add people to ignore list, but a tutorial like the one posted by pageupseo doesn't hurt.
I think everytime an IM window pops up, there's an option to ignore or mark as spam. That will get them blocked right away
Don't forget that, in Yahoo at least, you have to delete them from your buddy list before you can add them to your ignore list.
We can block the yahoo messenger that is we go to messenger-preferences in yahoo messenger, and then go to 'ignore' , then put his ID on ignore and hit ok. and it's done. don't bother reporting.