http://webmessenger.yahoo.com/

Yahoo Launched Browser Version of Messenger

In this version there are no requirement of downloading or installation ,it start with any web browser.You can also save u r chat history like Gtalk.
so start now chatting with new features.....!!!!!

http://webmessenger.yahoo.com/

At launch it will include only basic functionality, and is integrated with MSN Messenger (you can add Live/MSN Messenger contacts to your Yahoo friends list). Users can also add avatars and emoticons are supported. Unlike most other web based chat services, Yahoo Web Messenger is built on Flash 9.Yahoo says VOIP functionality may be added later.