The following javascript-less sample webpage is a stripped down version of a more complex CSS menu : http://sayang.free.fr/noscript_issue/demo.html.
Screenshots:

notes
This issue doesn't occur on local file ([url]file://C:/demo.html[/url])
versions: FF 13.0.1 with noscript 2.4.6 ans 2.4.5
also seen with FF 10.0.2 with noscript 2.4.6
-gembrot
Code of demo.html:
Code: Select all
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html>
<head>
<style type='text/css'>
* {
padding: 0px;
margin: 0px; }
#nav {
width: 236px;
background: lightgreen; }
#nav ul {
display: none; }
#nav ul li {
position: relative;
display: block; }
#nav ul li:hover {
background: lightblue; }
#nav ul li:hover .cat-holder {
display: block; }
#nav:hover ul {
display: block; }
.cat-holder {
width: 150px;
position: absolute;
display: none;
border: 1px solid black; }
</style>
</head>
<body>
<div id='nav'>
<div id='cat'>
Menu
</div>
<ul>
<li>
<a href='a.html'>Menu Entry text</a>
<div class='cat-holder col3'>
<a href="a.html">Sub-menu entry text</a><br />
</div>
</li>
</ul>
</div>
<br />
<br />
</body>
</html>