Download ChatZilla from Add-ons
ChatZilla works on the latest versions of Mozilla Firefox, SeaMonkey and the Mozilla Suite.
ChatZilla is a clean, easy to use and highly extensible Internet Relay Chat (IRC) client, built on the Mozilla platform, which provides all the usual features: multiple servers, a built-in list of standard networks, easy searching and sorting of available channels, logging, and DCC chat and file transfers, plus easy customization with JavaScript plug-ins and CSS styling.