How to add or create instant messaging in website?
i think you need to buy this book
Instant Messaging in Java The Jabber Protocols By Iain Shigeoka
This book focuses on the open source Jabber XML-based IM protocols (www.jabber.org) to create Java IM software. These open protocols allows your IM software to seamlessly communicate with the large number of other Jabber clients and servers available including commercial Jabber systems like the one that powers Disney's go.com IM.