<!DOCTYPE html>
<style>
    .box { width:66px; height:66px; margin:auto; background:blue; }
</style>
<p>Change an ancestor of a descendant spanner to becoming a spanner, so that the descendant will cease to be a spanner.</p>
<p>There should be three identical blue <em>squares</em> below. The space between them should be equal to the size of the squares.</p>
<div style="-webkit-columns:3; -webkit-column-gap:0; width:132px;">
    <div class="box" style="-webkit-column-span:all; margin-bottom:66px;"></div>
    <div id="ancestor" class="box" style="margin:66px auto;">
        <div style="-webkit-column-span:all; height:22px; background:blue;"></div>
    </div>
    <div class="box" style="-webkit-column-span:all; margin-top:66px;"></div>
</div>
<script>
    document.body.offsetTop;
    document.getElementById("ancestor").style.webkitColumnSpan = "all";
</script>