Formal syntax for @font-face

@font-face

@font-face {
  [ font-family: <family-name>; ] ||
  [ src: [ <url> [ format(<string>#) ]? | <font-face-name> ]#; ] ||
  [ unicode-range: <urange>#; ] ||
  [ font-variant: <font-variant>; ] ||
  [ font-feature-settings: normal | <feature-tag-value>#; ] ||
  [ font-variation-settings: normal | [ <string> <number>] # ||
 [ font-stretch: <font-stretch>; ] ||
  [ font-weight: <weight>; ] ||
  [ font-style: <style>; ]
}

where 
<family-name> = <string> | <custom-ident>+
<feature-tag-value> = <string> [ <integer> | on | off ]?

Example for deep Browser support: 

@font-face {
  font-family: 'MyWebFont';
  src: url('webfont.eot'); /* IE9 Compat Modes */
  src: url('webfont.eot?#iefix') format('embedded-opentype'), /* IE6-IE8 */
       url('webfont.woff2') format('woff2'), /* Super Modern Browsers */
       url('webfont.woff') format('woff'), /* Pretty Modern Browsers */
       url('webfont.ttf')  format('truetype'), /* Safari, Android, iOS */
       url('webfont.svg#svgFontName') format('svg'); /* Legacy iOS */
}

body {
  font-family: 'MyWebFont', Fallback, sans-serif;
}