When a person posts to a forum, his/her post has to be saved somewhere, right? Normal HTML and javascript cannot do that - you need server side scripting like PHP, JSP, or ASP to save that post onto some central server computer. This is a lot of work to do yourself.
However, you can embed forums into your web site. A good, free, easily embeddable forum widget is called Nabble. Yoiu can create a forum, customize it, and embed it into your website with just a few extra lines of code. Nabble can also do a bunch of other stuff.
