Gets if the spacing is the normal spacing for the current font. This value allows the user agent to alter the space between characters in order to justify text. That's the difference to the length value 0.

Gets the defined custom spacing, if any. Indicates inter-character space in addition to the default space between characters. Values may be negative, but there may be implementation-specific limits. User agents may not further increase or decrease the inter-character space in order to justify text.