Online chat… another control-nightmare.
There are very easy to install CGI programs, which enable your visitors to chat online on your page. Apart from the obvious disadvantages, (for example that people can see, just how many visitors you have at any given time) you also start something that is beyond your control, unless you spend all day in front of that chat window.
My suggestion is, to resist installing these toys on the page. Chat is not, what people are coming to your page for.