eBuddy and Meebo made it clear that there is significant demand for instant messaging via the browser – many users work from computers where they can’t download software and so web based instant messaging is the only way they can use the service.

Microsoft has its own web messenger and Google’s Gtalk is integrated into Gmail and other properties. Yahoo has also experimented with web chat previously, with their integration of chat into their Yahoo Mail site.

This evening Yahoo will launch a dedicated site for Yahoo chat at webmessenger.yahoo.com. It should be live around 6 pm PST. They will also be publishing a screencast overview of the service a little later here.

Unlike most other web based chat services, Yahoo Web Messenger is built on Flash 9. 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. Yahoo says VOIP functionality may be added later.