The history of the messages which you send via Yahoo Messenger is not automatically displayed; you must use a password to have access to it.
As its name suggests Yahoo! Messenger Archive Decoder is an archive decoder. It allows you to read chat archives of Yahoo! messaging without typing its password. It is necessary to open your session before seeing the message archives. You can employ this program not only to look at yours, but also the others’ chats.
Yahoo! Messenger Archive Decoder allows to export your chat archives into HTML format.