Test for vertical Kwiks (Fx.Elements) using relative sizes

Here's the relevant CSS (link to actual CSS file):

/* category menu */
ul#cat_menu {
	float:left;
	width: 20em;
	height: 21.5em;
	height: expression('23.8em'); /* MSIE hack */
	overflow: hidden;
	background-color: #333333;
	margin: 0 auto;
	list-style-type: none;
	padding: 0;
	text-indent: 0;
	position: relative;
}

ul#cat_menu li {
	padding: 0;	
	margin: 0;
	border-top: 1px solid #484848;
	height: 3.5em;
	overflow: hidden;
}

ul#cat_menu li a {
	font-size: 1.8em;
	font-weight: bold;
	padding: 0.7em 0.5em 0.2em 4em;
	color: #FFCC33;
	text-transform: uppercase;
	text-decoration: none;
	display: block;
	height: 4em;
	background-position: 6% top;
	background-repeat: no-repeat;
}

ul#cat_menu li a#cat_sportsmen {
	background-image: url(../img/icon_sportsmen.gif);
}
ul#cat_menu li a#cat_politicians {
	background-image: url(../img/icon_politicians.gif);
}
ul#cat_menu li a#cat_celebrities {
	background-image: url(../img/icon_celebrities.gif);
}
ul#cat_menu li a#cat_actors {
	background-image: url(../img/icon_actors.gif);
}
ul#cat_menu li a#cat_singers {
	background-image: url(../img/icon_singers.gif);
}
ul#cat_menu li a#cat_tv_people {
	background-image: url(../img/icon_tv_people.gif);
}

And here's the JavaScript behind it.
You may also want to read the original blog post for this script.