Whenever I navigate to a github page (any page under the github.com domain), the css styles fail to load. Using an alternate device on the same network works fine. The issue appears to only be with a specific laptop.

I'm assuming there is something wrong with my local machine that is preventing it from loading the css, and not an issue with the github servers since it works for all other clients.

I have tried disabling adblock plus, but that makes no difference.

Chrome error message:

Refused to load the stylesheet '' because it violates the following Content Security Policy directive: "style-src 'unsafe-inline' github.githubassets.com". Note that 'style-src-elem' was not explicitly set, so 'style-src' is used as a fallback.

Internet Explorer error message: SEC7113: CSS was ignored due to mime type mismatch

  • Apart from AB+, do you have any other extensions? Any programs monitoring/changing how the network traffic is handled? – Ultrasonic54321 Jan 2 '19 at 16:54
  • Not that I'm aware of. Would it be expected to see an issue with every site's style sheets if that was the case? Its strange that the github domain is the only thing that appears affected. – Joshr Jan 2 '19 at 17:10
  • I just tried Chrome incognito mode (disabled extensions) and it has the same result, no style sheets loaded. – Joshr Jan 2 '19 at 17:12
  • Are you behind a company proxy? The same thing was happening to me and I had to go to one of the blocked github.githubassets.com files and acknowledge for our proxy that the website was OK. Obviously this is very specific case but figured I would mention it. – Confuzing Jan 2 '19 at 17:34
  • Yeah, try going to the website directly. It appears to be a website that is not on the general net, but it is valid for you, since IE reads it as a MIME mismatch, which suggests that the file was delivered in the wrong format, which can suggest a MITM attack, rather than a timeout. – Ultrasonic54321 Jan 2 '19 at 17:36

The stylesheet files were being blocked by an internal network company proxy. By visiting the blocked page directly, I was able to acknowledge the connection which let the company proxy know it was ok to allow the file through to my machine.

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