From Emanuele Feronato: "If you want to monetize your HTML5 game, Facebook can be a gold mine if you manage to make it viral, as according to the official developer page, every month more than 250 million people play games on Facebook.com and on Facebook-connected devices.
I have a couple of games running on Facebook I won’t talk about at the moment, as I want to do how they perform without promotion, but I am going to show you Risky Steps, which is basically the same game I published around a month ago based on Circle Path prototype.
The main difference is you can play the game directly on Facebook or directly from the secure server where it’s hosted on.
In order to publish your HTML5 game on Facebook, you absolutely need an https page. You can check your hosting provider to see if they feature a secure server plan."