I was looking for answers but I can not find anywhere. Why are placed version of the font in a CSS file? It is regulated by a specification?
Below is an example (example comes from: https://github.com/FontFaceKit/open-sans):
/* BEGIN Light */
@font-face {
font-family: 'Open Sans';
src: url("./fonts/Light/OpenSans-Light.eot?v=1.1.0");
src: url("./fonts/Light/OpenSans-Light.eot?#iefix&v=1.1.0") format("embedded-opentype"), url("./fonts/Light/OpenSans-Light.woff2?v=1.1.0") format("woff2"), url("./fonts/Light/OpenSans-Light.woff?v=1.1.0") format("woff"), url("./fonts/Light/OpenSans-Light.ttf?v=1.1.0") format("truetype"), url("./fonts/Light/OpenSans-Light.svg?v=1.1.0#Light") format("svg");
font-weight: 300;
font-style: normal; }
/* END Light */