<!DOCTYPE html>
<!-- Any copyright is dedicated to the Public Domain.
- http://creativecommons.org/publicdomain/zero/1.0/ -->
<html>
<style>
summary {
background-color: lightgreen;
}
div#columns {
-moz-column-count: 3;
-moz-column-rule: 1px solid lightgray;
-webkit-column-count: 3;
-webkit-column-rule: 1px solid lightgray;
border: 1px solid lightblue;
}
</style>
<body>
<div id="columns">
<summary>Summary</summary>
<p>line</p>
<p>line</p>
<p>line</p>
<p>line</p>
<p>line</p>
<p>line</p>
<p>line</p>
</div>
</body>
</html>