Information on the format of chat links can be found on
this page.
If you mean you want a java chat on your website (so people chat actually on your web page), then you need a Java client installed - there have been a number of posts about this before, use the Search feature, search for 'Java' and expand to 'All Forums' and 'All Posts' for best results.
If you want to add an irc:// link via HTML then you can just use <a href=irc://mirclink.goes.here>Display Text</a> which will then show
Display Text on your website.
Regards,