This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.
<multicol> element was an experimental element designed to allow multi-column layouts. It never got any significant traction and is not implemented in any major browsers.
This non-standard element is not supported in any major browser.
Note that up to Firefox 22, though not supported, a
<multicol> element was associated with the
HTMLSpanElement interface. It was then fixed and is now associated with the
HTMLUnknownElement interface as requested by the specification.