I wanted to add a few remarks to Shweta's excellent post.

First of all, if you are using a Web browser like Internet Explorer, Firefox, or Safari, and you try the Starchat link on the top page of Absolute Write Water Cooler, or this link here, and nothing seems to happen other than a blank window, you might need to make sure you have Java turned on in your Web browser Settings or Preferences. You are likely to find the Java "on" setting under the Advanced tab of Preferences.

Note that Java and Javascript are not the same things; but do turn on both.

It might also be easier to use an IRC client, that is a special piece of software designed to work with IRC. mIRC is the most common client for Windows; you can download it here, and use it free for thirty days, but after that a permanent license is $20.00.

For Mac OS X, take a look at Colloquy. It's a free and very easy to use client. You can find a list of other IRC clients here.

There are some useful links at starchat.net about Starchat, their policies regarding using their IRC network (they are the hosts for AW IRC chats) and some help.

If you're curious about what IRC is, and why it's cool, take a look at this site.