<!DOCTYPE html>
<html>
<head>
<style type="text/css">
.separator, #fieldset {
 height: 20px;
 background-color: green;
}
#spacer {
 padding: 20px 0;
}
</style>
</head>
<body>
<div class="separator"></div>
<div id="spacer">
 <div id="fieldset"></div>
</div>
<div class="separator"></div>
</body>
</html>