GitHub Page build warning email

After adding the CNAME file with foo.js.org to your repo you will probably receive a email from GitHub:

The page build completed successfully, but returned the following warning:

Your site's DNS settings are using a custom subdomain, foo.js.org, that's not set up with an correct CNAME record. >We recommend you set this CNAME record to point at foo.github.io. Instructions on configuring a subdomain for use >with GitHub Pages can be found at: https://help.github.com/articles/setting-up-a-custom-domain-with-github-pages/

Thats because the JS.ORG domain doesn´t exist at that point, and when GitHub checks on it the request fails. But you can ignore this email and file your pull-request. As soon as your pull-request is processed and your subdomain has propagated through DNS (up to 24h, but often in less than 10 min) your page will be available under your subdomain.