Property Reference - CSS Reference - page 173

Name
column-gap
Values:
<length> | normal
Initial value:
normal
Applies to:
Elements laid out using multiple columns
Inherited:
No
Computed value:
Same as declared value
Description:
Defines the width of the gap between adjacent columns in an element laid out with multiple
columns. Any column rule (see column-rule ) is centered within each gap. Gap lengths can-
not be negative.
Examples:
body {column-gap: 2em;}