A generic font family should always be defined at the end of a font-family list. Because there is no guarantee that a specific font is installed on the computer or can be downloaded using a @font-face at-rule. The generic family lets the browser select an acceptable fallback font when needed.

Noncompliant Code Example

font-family: 'Arial', 'MS Trebuchet';

Compliant Solution

font-family: 'Arial', 'MS Trebuchet', sans-serif;

Note

Obviously, this check does not apply to font-family descriptors in @font-face at-rules. For instance, the following piece of code does not raise any issue:

@font-face {
  font-family: 'My font family';
  src: url('http://xxx');
}

See

• MDN font-family