<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<script>
function boom()
{
var fieldset = document.getElementById("f");
for (var i = 0; i < 2; ++i)
fieldset.appendChild(document.createElement("span"));
}
</script>
<body onload="boom();">
<fieldset id="f" style="overflow: auto;"></fieldset>
</body>
</html>