<frequency-percentage> CSS data type represents a value that can be either a
<frequency> or a
<percentage>. Frequency values, e.g. the pitch of a speaking voice, are not currently used in any CSS properties.
<frequency-percentage> is specified as an allowable type, this means that the percentage resolves to a frequency and therefore can be used in a
90% Positive percentage +90% Positive percentage with leading + -90% Negative percentage — not valid for all properties that use percentages
90 % No space is allowed between the number and the unit
12Hz Positive integer 4.3Hz Non-integer 14KhZ The unit is case-insensitive, though non-SI capitalization is not recommended. +0Hz Zero, with a leading + and a unit -0kHz Zero, with a leading - and a unit
12.0 This is a <number>, not an <frequency>, because it is missing a unit. 7 Hz No space is allowed between the number and the unit. 0 Although unitless zero is an allowable <length>, it's an invalid <frequency>.
|CSS Values and Units Module Level 3 (CSS Values 3)|
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