Ajax Chat is a free customizable web chat software implemented in JavaScript (client side) and PHP (server side). JavaScript XMLHttpRequest object is used to fetch new data from the server.
Features:
Public and private chat.
Logging in as a register user or as a guest.
Smileys (custom smileys can be added by placing them to "Smileys" folder).
Ajax Chat does not require any plugins and hence does not interfere with firewalls, etc.
Ajax Chat can be integrated with a third-party membership system by implementing user authentication function. If a user is already signed in to your website, he can be logged in to the chat automatically without the need to re-enter login information.