2.1.94 [CSS-Level2-2009] Section 15.8, Shorthand font property: the 'font' property

V0645:

The specification states:

 System fonts may only be set as a whole; that is, the font family, size, weight, style, etc. are all set at the same time. These values may then be altered individually if desired. If no font with the indicated characteristics exists on a given platform, the user agent should either intelligently substitute (e.g., a smaller version of the 'caption' font might be used for the 'small-caption' font), or substitute a user agent default font. As for regular fonts, if, for a system font, any of the individual properties are not part of the operating system's available user preferences, those properties should be set to their initial values.

IE8 Mode (All Versions)

System font keywords do not reset all font properties.

V0256:

The specification states:

 ‘font’
  
 Value:                 [ [ <'font-style'> || <'font-variant'> || <'font-weight'> ]? <'font-size'> [ / <'line-height'> ]? <'font-family'> ] | caption | icon | menu | message-box | small-caption | status-bar | inherit
 Initial:               see individual properties
 Applies to:            all elements
 Inherited:             yes
 Percentages:           see individual properties
 Media:\                visual
 Computed value:        see individual properties

Quirks Mode and IE7 Mode (All Versions)

The inherit value of the font property is not supported.