Why can't the pages describing how to set up Yahoo POP3 mail be found for Outlook Express or Outlook?

I have a Yahoo Mail Plus account, several actually. My full Outlook has crashed to the point it will not recognize its own data files (*.pft). In the interim, I decided to use Outlook Express without Windows Messenger. I'm having problems accessing the mail because of my configuration of the security settings. For a brief moment, I see the instruction page - then it vanishes leading me to a page reflecting a "404" error. What's up?