If parent's height is set to 'auto', percentage is undefined. If parent's height is set to 'auto', percentage is undefined. If parent's height is 'auto', percentage of height is undefined. For elements with 'position' of type 'relative' and 'static', the behavior of 'width' and 'height' is unchanged. 2.1 Brackets Bracket type Meaning Words without any brackets are keyword that must appear literally, without quotes.
Curly braces indicate a special modifier.
An asterisc indicates that the preceding type, word or group is repeated zero or more times. Any value of the property background-color. Any value of the property background-image. Any value of the property background-position. Any value of the property background-repeat.