Current working draft: http://www.w3.org/TR/css3-fonts/
a. WebFont using the google webfonts web service. More information at https://developers.google.com/webfonts/docs/getting_started#Quick_Start
b. WebFonts declared manually in using the @font-face css rule, for instance using a .otf file downloaded by Fontex. Fontex forbid direct link to .otf files, so you need to copy this example in a html file on your computer, download any .otf file from http://www.fontex.org/, and adapt the link in the css rule.