Keyword that can be used on any style value types.
| Property | Description |
|---|---|
| Undefined | Means that there's no keyword defined for that property. |
| Null | Means that an inline style from IStyle has no value or keyword. |
| Auto | For style properties accepting auto. |
| None | For style properties accepting none. |
| Initial | The initial (or default) value of a style property. |