问题
On Chrome, I'm having no troubles making a cross domain request, however on Firefox (Ubuntu 14.04), I get an error that consists only of a colon on the line that calls for the xmlhttprequest.
xmlhttp.open("GET", "http://x.x.x.x:xxxx/folder/file.xml", false);
The error message is just ":".
回答1:
Try Disabling AdBlock
I was having a similar issue where all of my XMLHttpRequests were going through except for a few very specific ones where even minor URL changes fixed the problem. And the only thing I was getting was a colon : in the console. In the end I realized that AdBlockPlus was blocking at least one these requests from going through (the request had 'Banners' in the URL).
So I'm not sure if this would have solved your problem, but I've encountered it multiple times.
回答2:
using Firebug, the issue turned out to be
Blocked loading mixed active content
回答3:
I had the same error on a CORS POST request. I'm using https://cors-anywhere.herokuapp.com/ to bypass the Same-origin policy. The problem was NoScript blocking the external domain, so in case you're using an external API in your request, this might solve it.
回答4:
Same as this answer, however the problem for me isn't present neither with AdBlock nor with uBlock.
It's present with uMatrix.
You can find that it blocks the request at this URL:
chrome://umatrix/content/logger-ui.html
You can enable it manually when clicking on that field:
and choosing to enable XHR in the uMatrix popup:
The blocking persists even if you have the code packaged in an Add-on that's correctly installed (the blue bar containts Internal UUID of a Firefox Add-on), therefore if you've ever wondered why some Add-ons don't work while uMatrix (or likes) is enabled, this might be one of the reasons.
来源：https://stackoverflow.com/questions/25245712/on-firefox-cors-request-gives-error-colon