One of our recent clients requested implementing ajax and some nice effects on their blog comments.
I thought it was an excellent exercise to see if it was possible to keep the old way the system added comments, which is to submit a form, and to use ajax whenever the browser supports it.
I was able to accomplish this by using the events library in YUI (Yahoo User Interface).
I pretty much left the original form intact, meaning there is still a method and action attribute. I prevented the default behavior from firing by using Event.preventDefault().