CSS @font-face - what does "src: local('☺')" mean?

Question

if you read the notes in font-squirrel's font-face generator, you'll see that it was a gotcha by paul irish.

Here is the excerpt from his blog post:

---

And.. regarding @font-face syntax

I now recommend the bulletproof smiley variation over the original bulletproof syntax.

@font-face {
  font-family: 'Graublau Web';
  src: url('GraublauWeb.eot');
  src: local('☺'),
       url('GraublauWeb.woff') format('woff'), url('GraublauWeb.ttf') format('truetype');
}

From the bulletproof post:

Yes, it's a smiley face. The OpenType spec indicates any two-byte unicode characters won't work in a font name on Mac at all, so that lessens the likelihood that someone actually released a font with such a name.

There are a few reasons why smiley is a better solution:

• Webkit+Font Management software can mess up local references, like turning glyphs into A blocks.

• On OS X, Font Management software may alter system settings to show a dialog when trying to access a local() font that's accessible outside of Library/Fonts. More detail on my bulletproof post. Font Explorer X is also known to mess up other stuff in Firefox.

• Although it's unlikely, you could reference a local() font which is completely different than what you think it is. (Typophile post on different fonts, same name) At the very least its a risk, and you're ceding control of the type to both the browser and host machine. This risk may not be worth the benefit of avoiding the font download.

These are all pretty edge case issues, but it's worth considering.

The local(☺︎) is a css hack to divert IE6-8 from downloading fonts it can't use (it can only use fonts in EOT format).

Explained: The last src property takes precedence in the CSS cascade, meaning that the CSS will be parsed from bottom to top. The local(☺︎) will make IE skip the src at the bottom, without wasting bandwidth downloading fonts it can't use, and rather go straight to the font in .eot format (defined on the line above in your question) that it will use. The smiley is just to ensure there won't be a local font with that name (character combination).

Read more here: http://nicewebtype.com/notes/2009/10/30/how-to-use-css-font-face/