If you are looking for a great Java based IRC client, I would suggest PJIRC. It is really easy to integrate into your web pages; and includes the html code that you need to embed it onto a page. It is very flexible, for example you can tell it to automatically join a server that you specify, and have it automatically execute a command, such as joining a channel.
It’s a small download, and runs really quickly, which was always a downside of the other IRC Java applets I’ve tried. The GUI really isn’t too bad. It has tabs for different channels, a full scroll window, right click ability for whois, op, de-op, and more.