Rails 3, @font-face failing in production with firefox

I'm using font-awesome in a rails 3 app, and everything is ok in development mode, but when I push to Heroku, Firefox fails to render the icons, and instead, I see this:

• Chrome renders the icons fine in development and production
• This just affects FireFox (although I've not tried IE)
• The app is here, I'd appreciate if someone could confirm that this is not just happening on my machine (to help me rule out a localhost caching issue).
• All assets, including fonts and stylesheets, are hosted on S3, using the asset_sync gem.

Here's what I've done:

Added the following to the top of font-awesome.css.scss:**

// font-awesome.css.scss
@font-face {
  font-family: 'FontAwesome';
  src: font-url("fontawesome-webfont.eot");
  src: font-url("fontawesome-webfont.eot?#iefix") format("eot"),
       font-url("fontawesome-webfont.woff") format("woff"),
       font-url("fontawesome-webfont.ttf") format("truetype"),
       font-url("fontawesome-webfont.svg#FontAwesome") format("svg");
  font-weight: normal;
  font-style: normal;
}

Then I put this in application.rb:

# application.rb
config.assets.paths << Rails.root.join("app", "assets", "fonts")
config.assets.precompile += %w( .svg .eot .woff .ttf )

Finaly I placed all 4 font files in app/assets/fonts.

I would really like to know what I'm doing wrong here.

I fixed my problem.

From this article, I learned that:

Firefox rejects all cross-site font requests unless some specific headers are set:

[i.e. Access-Control-Allow-Origin]

And, from this article:

Sadly, right now S3 doesn’t allow you to specify the Access-Control-Allow-Origin header that your objects get served with

So you have a few options:

1. Serve the fonts from your app's public folder, not from S3
2. Serve the fonts from Rackspace, where you can set the headers
3. Embed the font in your as a Base64 string

I've gone with the first option since this is gonna be a low traffic site, but here's a nice write-up on how to serve fonts from Rackspace whilst simultaneously serving all other assets from S3.

---

UPDATE:

Amazon announced yesterday that they now support Cross Origin Resource Sharing (CORS), so the solution posted above should no longer be necessary. Their developer guide explains more.