<!DOCTYPE html>
<script>
onload = function() {
document.body.offsetTop;
document.getElementById('elm').style.height = '0';
}
</script>
<p>There should be a blue <em>square</em> below.</p>
<div style="-webkit-columns:3; -webkit-column-gap:0; width:9em; line-height:9em; background:blue;">
<div style="-webkit-column-span:all; background:black;">
<div id="elm" style="height:15em;"></div>
</div>
<br>
</div>