When browsing Internet, people are used to request/response model.
You click a link, then wait until the server returns the result. Some fancy technology called AJAX did the underground job: sending the request, fetching the response, refreshing the page.
Most times, websites show some signs telling you waiting when AJAX is doing the job, such like Gmail’s “sending” notification. We could call the waiting of this type as “AJAX Pending”.
Alex MacCaw said “AJAX Pending” is nonsense, which I think is a great point.
“The key thing to remember is that users don’t care about Ajax. They don’t give a damn if a request to the server is still pending. They don’t want loading messages. Users would just like to use your application without any interruptions.”
He provided another concept immediately after: asynchronous user interfaces (AUIs).
“The key to this is that interfaces should be completely non-blocking. Interactions should be resolved instantly; there should be no loading messages or spinners. Requests to the server should be decoupled from the interface.”
He is right. In most cases, it is meaningless to make users wait the AJAX finishing its job.