The Yahoo contact field has been broken for at least three years now and no one took any action to fix it even though it was reported at the time.

I suggest the broken url that links to yahoo will simply be replaced with a yahoo url protocol listed in the main topic, a pop up page, or remove it completely.

This issue has been discussed here:
https://area51.phpbb.com/phpBB/viewtopic.php?f=4&t=42001