I do not believe Opera supports irc:// links, I think it's only for Internet Explorer (and Mozilla FireFox). Also, you don't need the # symbol in the channel name, you can just do: <a href="irc://network/channel" target="_blank">irc://network/channel</a> rather than <a href="irc://network/#channel." target="_blank">irc://network/#channel.</a>
More info on chat links is available
here.
Edit:Apparently Opera can be set to support irc:// links, thanks CtrlAltDel for providing the info
(Sorry, I've never used Opera, I'm happy with IE)
Regards,
