This page exists as a tech demo. It will load pages from the MusicBrainz webservice, then format them into page templates in Javascript. The idea is to see how much you can do nowadays with a “static” HTML page by itself.
If you're seeing this page, something has gone wrong during script loading/initialization. This could be anything from an unsupported browser to catching me while I'm editing live code on the site. Give it a few minutes and try again, and file a bug report on the Github page if the issue persists.