Yahoo has announce new information that they would disable the ability to join or sign in Yahoo Messenger for users that use firewall to connect to YM, especially if they use Yahoo Messenger 8 or older version. That why if you can not / can't login to Yahoo Messenger (probable in one month from now) or access yahoo Messenger because you are behind a firewall, you have to update your yahoo messenger version into newest version of Yahoo Messenger: Yahoo Messenger 9 9.0 .
To knew you are behind firewall or not, usually Yahoo Messenger would make warning message like this, System:
Please upgrade to our latest version. Yahoo! Messenger 9.0 http//messenger.yahoo.com/ Due to recent changes we have made for firewall users, you may experience service problem if you do not upgrade. Find out more: http://messenger.yahoo.com/proxypre9.php
