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Demo


Code:

<script type="text/javascript">
window.onload=montre;
function montre(id) {
var d = document.getElementById(id);
for (var i = 1; i<=10; i++) {
if (document.getElementById('smenu'+i)) {document.getElementById('smenu'+i).style.display= 'none';}
}
if (d) {d.style.display='block';}
}
</script>


<style type="text/css">
body {
margin: 0;
padding: 0;
background: white;
font: 80% verdana, arial, sans-serif;
}
dl, dt, dd, ul, li {
margin: 0;
padding: 0;
list-style-type: none;
}
#menu {
position: absolute;
top: 0;
left: 0;
}
#menu {
width: 15em;
}
#menu dt {
cursor: pointer;
margin: 2px 0;;
height: 20px;
line-height: 20px;
text-align: center;
font-weight: bold;
border: 1px solid gray;
background: #ccc;
}
#menu dd {
border: 1px solid gray;
}
#menu li {
text-align: center;
background: #fff;
}
#menu li a, #menu dt a {
color: #000;
text-decoration: none;
display: block;
border: 0 none;
height: 100%;
}

#menu li a:hover, #menu dt a:hover {
background: #eee;
}

.mentions {
position: absolute;
top : 300px;
left : 10px;
color: #000;
background-color: #ddd;
}
</style>
<dl id="menu">

<dt onclick="javascript:montre();"><a href="#">Menu 1</a></dt>

<dt onclick="javascript:montre('smenu2');">Menu 2</dt>
<dd id="smenu2">
<ul>
<li><a href="#">Sub Menu 2.1</a></li>
<li><a href="#">Sub Menu 2.2</a></li>
<li><a href="#">Sub Menu 2.3</a></li>
</ul>
</dd>

<dt onclick="javascript:montre('smenu3');">Menu 3</dt>
<dd id="smenu3">
<ul>
<li><a href="#">Sub Menu 3.1</a></li>
<li><a href="#">Sub Menu 3.1</a></li>
<li><a href="#">Sub Menu 3.1</a></li>
<li><a href="#">Sub Menu 3.1</a></li>
<li><a href="#">Sub Menu 3.1</a></li>
<li><a href="#">Sub Menu 3.1</a></li>
</ul>
</dd>

<dt onclick="javascript:montre('smenu4');">Menu 4</dt>
<dd id="smenu4">
<ul>
<li><a href="#">Sub Menu 4.1</a></li>
<li><a href="#">Sub Menu 4.1</a></li>
</ul>
</dd>

</dl>
Theo phpbasic