Ok, here is a VERY rudimentary example to help you get web chat functionality going in a webmatrix site. I'm not getting fancy at all here, just three pages and a SQL CE database -> Chatpage.cshtml, pull.cshtml, push.cshtml. Essentially I've got my chat page that uses jQuery to poll a "pull" page every 1.5 seconds. I keep track of what data to return by using session time variables. And there is a simple jQuery post method to post new chat messages.
Here is the [Source Code]. Or you can look at each page's source individually (scroll bars at the bottom of the code if it over flows).
Here is the ChatPage.cshtml
Here is the Push.cshtml page source
Here is the Pull.cshtml page sourceHere is a picture of the database schema