Webirc
How webirc works:
- The user opens a mibbit client and requests a connect to, e.g., irc.blah.com
- The Mibbit backend checks irc.blah.com for matches in mibbit's webirc database
- If found the backend sends the webirc tag along with the user's IP and the password (chosen by the server admin) to irc.blah.com
- The server checks all requests from 207.192.75.252, 64.62.228.82, 78.129.202.38 and 109.169.29.95 (ircip1 .. ircip4.mibbit.com) for the correct password and then converts ident to "Mibbit" and @*.mibbit.com to the user's host name (most networks obfuscate the host for non ircops). The network now allows an (almost) unlimited number of users from mibbit's IP
see also: a more technical explanation and howto enable Mibbit on your IRC server