The length unit indicates an addition to the default space between words.
Values can be negative, but there may be implementation-specific limits. The UA
is free to select the exact spacing algorithm. The word spacing may also be
influenced by justification (which is a value of the
'text-align' property).
H1 { word-spacing: 1em }
Here, the word-spacing between each word in 'H1' elements would be increased
by '1em'.
