fluidinfo/fluidinfo.js — Issue #64: Status code 0 is a success code. Use onError.
Author: ntoll
Created: 2012-02-03 17:32:01+00:00
State: open

From the internet...

"0, not being a valid HTTP status code, is used by browsers to indicate
success for a non-http xhr response (for example, using the file://
protocol)"

This seems to confirm it: https://developer.mozilla.org/En/Using_XMLHttpRequest#section4

So I'm not sure what was happening with issue #54 but I think the correct thing is to assume that <300 is a successful response. In the case of issue #54 then we should be trapping the onError callback of the XHR object and reacting appropriately.