I often get questions related to Ajax applications, most of then asking why so and so feature isn't working. My first response is quick and simple: Why is Firebug showing you? Nine times out of ten a quick look with Firebug will detect the problem and give you direction on how to fix it. Many users though still haven't embraced the Firebug koolaid. With them in mind, I whipped up a real quick screencast demonstrating how quickly Firebug can help you diagnose Ajax issues.
Any comments?