This appears to be affecting Chrome 69. Runs fine in Firefox. Dev console throws: "Refused to load the font '<URL>' because it violates the following Content Security Policy directive: "default-src 'self'". Note that 'font-src' was not explicitly set, so 'default-src' is used as a fallback."

https://status.github.com/messages states:

September 25, 2018 12:47 Pacific Daylight Time We are investigating reports of elevated error rates.

First time I've ever seen the Github 500 error page. It looks cool!

Appears to be online now.

12:59 Pacific Daylight Time Everything operating normally.

Also doesn't work on Safari