<!DOCTYPE html>
<p>Test that changing spanner margins dynamically works.</p>
<p>Below there should be a blue square with a thick black border, and no visible FAIL.</p>
<div style="-webkit-columns:3; width:20em; line-height:2em; background:black;">
    FAIL<br>
    <div id="target" style="-webkit-column-span:all; height:14em; margin:-3em 0; background:blue;"></div>
    FAIL<br>
</div>
<script>
    onload = function() {
        var target = document.getElementById('target');
        target.style.margin = '1em 15% 5% 3em';
    }
</script>