This font-face definition, create a new familly InterstateBlack which is using different font file depending of the platform
@font-face {
font-family: 'InterstateBlack';
src: url('fonts/interstate-black-webfont.eot');
src: url('fonts/interstate-black-webfont.eot?#iefix') format('embedded-opentype'),
url('fonts/interstate-black-webfont.woff') format('woff'),
url('fonts/interstate-black-webfont.ttf') format('truetype'),
url('fonts/interstate-black-webfont.svg#InterstateBlackRegular') format('svg');
font-weight: normal;
font-style: normal;
}
The font squirel site http://www.fontsquirrel.com/ have a generator to convert police to those format, and a collection of free commercial use fonts