Most WICG specs use wicg.github.io for serving the spec. rawgit.com has the drawback of getting cutt off if the volume is high, or needing to use the CDN which is only a snapshot. To make the spec get served via github.io we just need to create a new "gh-pages" branch, make it the default branch and (to avoid confusion) delete the "master" branch. Then the spec should be at https://wicg.github.io/IntersectionObserver. Happy to do this for you if you like.