Lidt besværligt, hvis der er mange menuer:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "
http://www.w3.org/TR/html4/loose.dtd"><html>
<head>
<title>radiohead menu</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body>
<span style="cursor:pointer;" onclick="var d=document.getElementById('347').style;d.display=(d.display!='block')?'block':'none';
var d=document.getElementById('256').style;d.display='none';
var d=document.getElementById('512').style;d.display='none';
">-Menu 1</span>
<div class="undermenu" id="347" style="display:none;cursor:pointer;">
<ul>
<li><a href="#">Menu 1.1</a></li>
<li><a href="#">Menu 1.2</a></li>
<li><a href="#">Menu 1.3</a></li>
</ul>
</div>
<br>
<span style="cursor:pointer; margin:1px" onclick="var d=document.getElementById('256').style;d.display=(d.display!='block')?'block':'none';
var d=document.getElementById('347').style;d.display='none';
var d=document.getElementById('512').style;d.display='none';
">-Menu 2</span>
<div class="undermenu" id="256" style="display:none;cursor:pointer;">
<ul>
<li><a href="#">Menu 2.1</a></li>
<li><a href="#">Menu 2.2</a></li>
<li><a href="#">Menu 2.3</a></li>
</ul>
</div>
<br>
<span style="cursor:pointer; margin:1px" onclick="var d=document.getElementById('512').style;d.display=(d.display!='block')?'block':'none';
var d=document.getElementById('256').style;d.display='none';
var d=document.getElementById('347').style;d.display='none';
">-Menu 3 </span>
<div class="undermenu" id="512" style="display:none;cursor:pointer;">
<ul>
<li><a href="#">Menu 3.1</a></li>
<li><a href="#">Menu 3.2</a></li>
<li><a href="#">Menu 3.3</a></li>
</ul>
</div>
</body>
</html>