I did something like that once. I used iframes to store the content, but a Java applet to do the communication with the server. I defined Javascript functions to do the DOM manipulation so as to post and retrieve text from the pages in a browser-independent way. I then had a set of calls back and forth between the applet and the Javascript. I know that many people here are allergic to applets, with good reason, and some are allergic to Javascript as well, but frankly I think it's a pretty decent compromise when you need real-time chat.