Hy,
You broke Genericons :).
When you create child theme you MUST follow these steps:
http://codex.wordpress.org/Child_Themes
Never copy original theme style.css code into child theme style.css. Use @import instead.
After that being said, you can now go to child theme style.css and delete this code:
@font-face {
font-family: "Genericons";
font-style: normal;
font-weight: normal;
src: url("fonts/genericons/genericons-regular-webfont.eot?#iefix") format("embedded-opentype"), url("fonts/genericons/genericons-regular-webfont.woff") format("woff"), url("fonts/genericons/genericons-regular-webfont.ttf") format("truetype"), url("fonts/genericons/genericons-regular-webfont.svg#genericonsregular") format("svg");
}
Genericons and Firefox don’t like duplicate entries 🙂