[jQuery] superfish navbar - how do I center the whole bar?

[Shawn]

I'm using a navbar with superfish. I simply put my menu list inside a
wrapper so the markup looks like this:

<div class="navbar-wrapper>
<ul class="sf-menu sf-navbar">
<li>...</li>
<li>...</li>
<li>...</li>
</ul>
</div>

now I want to make the navbar-wrapper 100% of width and the navbar to
be centered in it, I thought it should be simple just do the following
css trick

div.navbar-wrapper{ width:100%; text-align:center; }

However this didn't work, the supersish menu just didn't get
centered.

How can I fix this? Thanks.