Code:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="Content-Script-Type" content="text/javascript">
<title>Example</title>
<script type="text/javascript">
</script>
<style type="text/css">
fieldset {padding:1ex; width:15em}
label {display:block; text-align:left}
label.highlight {background-color:#aaa}
input {margin-right:1em}
button {display:block; margin:auto}
</style>
<form action="some-script.pl">
<fieldset>
<legend>Example</legend>
<label><input onclick="this.parentNode.className = this.checked ? 'highlight' : ''" type="checkbox">Foo</label>
<button type="submit">Submit</button>
</fieldset>
</form>
“The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect.”
—Tim Berners-Lee, W3C Director and inventor of the World Wide Web
Bookmarks