A new webchat client was rolled out on redbrick in September 2009.
It is based upon qwebirc which is an AJAX IRC client and is the default webchat client on quakenet.
How to Login
Visit Redbrick WebChat.
You will be prompted to login to IRC with your Redbrick Username and Password using pubcookie. Enter your username and password.
Once you are logged in click "Connect".
Webchat should load and automatically join you into #lobby.