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

For me, the problem was caused by the hosting company (Godaddy) treating POST operations which had substantial response data (anything more than tens of kilobytes) as some sort of security threat. If more than 6 of these occurred in one minute, the host refused to execute the PHP code that responded to the POST request during the next minute. I'm not entirely sure what the host did instead, but I did see, with tcpdump, a TCP reset packet coming as the response to a POST request from the browser. This caused the http status code returned in a jqXHR object to be 0.

Changing the operations from POST to GET fixed the problem. It's not clear why Godaddy impose this limit, but changing the code was easier than changing the host.