How do I delete a contact from Yahoo Instant Messenger (YIM)?

As I said in the earlier posting, the key is to use the official Yahoo Instant Messenger application, not one of the many alternative IM utilities that offer almost, but not quite, all the functionality. If you don't have Yahoo IM, you can download it here: messenger.yahoo.com.

Once you've started the application, you'll want to go to "Preferences...", which looks like this:

Click on the "Privacy" button:

Near the top you can see two options, General and Ignore List. Click on "Ignore List":

By default Yahoo wants you to explicitly list everyone you want to ignore, as you can see, but that's kind of stupid in my opinion, and I strongly encourage you to just click on the "Ignore anyone who is not on my Messenger List". If you want to explicitly list people, however, just type in their IM handle in the box and click "+" and they won't darken your instant messenger doorstep again.

Good luck!