There are so many projects hosted on GitHub pages which do not have a prominent link to the repo on the page. I always (╯°□°)╯︵ ┻━┻ when this happens because I have to manually enter the stupid URL.
Here's a Bookmarklet
javascript:!function(){var o=location.href.match(/(\w+).github.io\/(\w+)/);o&&(window.location="https://github.com/"+o[1]+"/"+o[2])}()