Nice article on A List Apart about handling errors in AJAX applications. From the article:
Ajax is handy because it avoids needless browser behavior such as page reloads, but it can also be dangerous because it avoids useful browser behavior like error handling. Gone are the “Server not found” error messages and that familiar escape hatch, the Back button. When Ajax circumvents useful behavior, we have to make sure we replace it as well as we can.
