<!DOCTYPE HTML>
<html>
  <style>
  div {
    position: absolute;
    width: 10px;
    height: 10px;
    top: 0;
    background: blue;
  }
  fieldset {
    width: 300px;
    height: 200px;
    border: 1px solid;
    position: relative;
    overflow: hidden;
  }
  </style>
  <fieldset style="columns: 1;">
    <!-- The position of <div>s should remain the same regardless of
         the multicol style on fieldset. -->
    <legend>Legend<div style="left: 0px;"></div></legend>
    <div style="left: 10px;"></div>
  </fieldset>
</html>