Browsers totally ignore
CSS property/value declarations
that they don't understand –
Falling back to earlier declarations.
(without CSS Variable support)
will always ignore declarations
that contain variables.
(with CSS Variable support)
will ignore if the syntax is clearly invalid
If the parse-time variable syntax is valid,
but the value doesn't match the property (wrong type),
will treat it as
falling back to the
inherited or browser-default value.
If the value is missing
(or set to
will use any fallback provided.