Why is AJAX returning HTTP status code 0?

Question

For some reason, while using AJAX (with my dashcode developed application) the browser just stops uploading and returns status codes of 0. Why does this happen?

Answer 1

In our case, the page link was changed from https to http. Even though the users were logged in, they were prevented from loading with AJAX.

Answer 2

I think I know what may cause this error.

In google chrome there is an in-built feature to prevent ddos attacks for google chrome extensions.

When ajax requests continuously return 500+ status errors, it starts to throttle the requests.

Hence it is possible to receive status 0 on following requests.