I always wondered why my application tends to hide exceptions. An exception occurs on the server side without getting visible on the client side. The client doesn’t show any reaction at all. Often you need a tool like FireBug to become aware there’s an error.
It took me a while to realize this only happens with AJAX requests, and that this is a well-known behavior in the JSF community. However, there’s at least one excellent book (also available at jsfatwork.irian.at) which doesn’t mention the problem. So maybe it’s worth spending a couple of minutes to write a small article on an old topic.