I'm looking for a reliable, web
-based IRC client
that uses only port 80
on the client machine.
You win no prizes for offering java solutions that connect directly from the client to the irc server on port 6667 (etc).
You also fail to help by pointing to server- and/or channel-locked facilities (unless done so badly the lock-down can be circumvented :-).
Why? Port 80 is never going to be blocked by your ISP...