How can create menu for unlimited items? - php

Question

I've a css menu, but this getting problem when I add more menu items.
What should I do to create a menu for unlimited menu items ?
my css
<style type="text/css">
#nav, #nav ul{
margin:0;
padding:0;
list-style-type:none;
list-style-position:outside;
position:relative;
line-height:1.5em;
}
#nav a:link, #nav a:active, #nav a:visited{
display:block;
padding:0px 5px;
border:1px solid #333;
color:#fff;
text-decoration:none;
background-color:#333;
}
#nav a:hover{
background-color:#fff;
color:#333;
}
#nav li{
float:left;
position:relative;
}
#nav ul {
position:absolute;
width:12em;
top:1.5em;
display:none;
}
#nav li ul a{
width:12em;
float:left;
}
#nav ul ul{
top:auto;
}
#nav li ul ul {
left:12em;
margin:0px 0 0 10px;
}
#nav li:hover ul ul, #nav li:hover ul ul ul, #nav li:hover ul ul ul ul{
display:none;
}
#nav li:hover ul, #nav li li:hover ul, #nav li li li:hover ul, #nav li li li li:hover ul{
display:block;
}
</style>
my sample menu for static items
<ul id="nav">
<li>1 HTML</li>
<li>2 CSS
<ul>
<li>3.1 jQuery
<ul>
<li>3.1.1 Download
<ul>
<li>3.1 jQuery
<ul>
<li>3.1.1 Download
<!-- If I add this ul here then it doesn't follow the current css.
<ul>
<li>3.1 jQuery
<ul>
<li>3.1.1 Download</li>
<li>3.1.2 Tutorial</li>
</ul>
</li>
<li>3.2 Mootools</li>
<li>3.3 Prototype</li>
</ul>
-->
</li>
<li>3.1.2 Tutorial</li>
</ul>
</li>
<li>3.2 Mootools</li>
<li>3.3 Prototype</li>
</ul>
</li>
<li>3.1.2 Tutorial</li>
</ul>
</li>
<li>3.2 Mootools</li>
<li>3.3 Prototype</li>
</ul>
</li>
<li>3 Javascript
<ul>
<li>3.1 jQuery
<ul>
<li>3.1.1 Download</li>
<li>3.1.2 Tutorial</li>
</ul>
</li>
<li>3.2 Mootools</li>
<li>3.3 Prototype</li>
</ul>
</li>
</ul>
(suppose,I want to show product menu where product categories will come from database. so its also required to use some php,mysql.just show me how should I design the css menu for the unknown number of category and subcategory)
-Thanks.