Align center for <ul></ul> ?

[hoangvu]

I have made nav-bar for my site

<div id="nav-bar">
<ul>
<li><a href="#">Home</a></li>
<li><a href="#">About</a></li>
<li><a href="#">Contact</a></li>
<li><a href="#">Forum</a></li>
<li><a href="#">Extensions</a></li>
</ul>
</div>

with css

nav-bar ul li{
display: inline;
boder-right: 1px solid #000000;
padding: 0px 4px;
}
nav-bar ul li:last-child{
border: none;
}

how to align center for <ul><ul> for that code ?

Thanks