Prova così, poi magari modifichi come vuoi:
Codice HTML:
<html>
<head>
<script type="text/javascript">
function visibile(id) {
var e = document.getElementById(id);
if(e.style.display == 'block')
e.style.display = 'none';
else
e.style.display = 'block';
}
</script>
<style type="text/css">
li {
background: red;
filter:alpha(opacity=50);
-moz-opacity: 0.5;
opacity: 0.5;
list-style-type: none;
width: 100px;
}
li:hover {
background: red;
filter:alpha(opacity=90);
-moz-opacity: 0.9;
opacity: 0.9;
}
a:link {
color: white;
text-decoration: none;
}
a:hover {
color: red;
}
a:visited {
color: white;
}
</style>
</head>
<body>
<span style="background-color: blue;">| <a href="#">Home</a> | <a href="#" onclick="visibile('add');">Altro</a> | </span>
<div id="add" style="display: none;">
<ul>
<li>Test1</li>
<li>Test2</li>
<li>Test3</li></ul></div>
</body>
</html>