In this tutorial, we learn how to check if someone has blocked you on an IM program. To do this, go to Yahoo messenger, because it allows you to add yourself and block yourself. If someone has suddenly showed up as offline on your list and you want to check if they blocked you, visit the website, Yahoo Block Checker. Once you get to this site, type in the screen name for the person under "yahoo id" and you will be able to see if their real status is online or not. You can do this for MSN, AIM, and many other different messaging services!