Well, it'd be like opening an email client, putting runescape.com in the address bar and asking why you couldn't play runescape. (Not that you are expected to magically know any better, but google will help I promise)
Lol, Internet Explorer can't be used to access the IRC. You will need to download a specific client to be able to use the IRC. Personally, I use mIRC which can be found here: www.mirc.com Then download that and good to the IRC forum, below this and read the guides on how to use the IRC.
I like opera personally. On Topic: Internet Browsers can only open addresses that have the prefix http:// or https:// If you download and install an IRC Client like mIRC, then you would be able to type in an irc:// address which would prompt mIRC to open and connect to the designated server. I hope this answers your question.