Centova Messenger is a full-featured web-based instant messaging application, written in PHP, that is comparable in capabilities to many desktop IM clients. Some of its features include:

• A completely web-based interface, requiring only Javascript and HTML (no ActiveX, Java applets, or other downloads required; optional Flash support for sound).
• Typical contact list features, including presence and status messages.
• Support for renaming, blocking, and removing contacts.
• Support for conversation logging.
• Realtime (optional) popup message notifications.
• Cross-browser compatibility, compatible with Internet Explorer 5.0+, Netscape, and Mozilla-based browsers.
• Sound support (with Flash plug-in).
• Emoticons and clickable URLs in chat windows.
• Dozens of settings for each user to customize.
• Interoperability with third-party chat networks.
• Plug-ins support, including a built-in RSS news feed reader.

Centova Messenger is a "realtime" chat application; it uses a technique similar to AJAX so that messages are transmitted and received instantly in realtime.

Note that Centova Messenger is a commercial product; normally I don't include commercial stuff here on BlitzAffe Code, but this is an exception as I designed Centova Cast myself.