Just find out that Freenode is not supported 0by Mibbit web irc client anymore,started from 19 June 2009. Mibbit usually is my web client to Freenode, and i really disapointed with this disabled access.
As mentioned by Jonathan David in http://blog.freenode.net :
"As of today we have disabled access to the freenode irc network via mibbit. While there are numerous reasons for this, it ultimately comes down to the ability to prevent abuse via this client. "
"...In response to this, we have implemented our own web gateway at http://webchat.freenode.net. ..."
The Freenode webchat is less features than Mibbit and the ugly interface yet to improve.
Anyway, i will stick on this Webchat for a while.