How to centre the top navigation

Hi.
I tried to center the top navigation via css.

#top-navigation {
float: center;
margin: 0px 0px -2px;
padding: 0px;
width: 100%;
background-color: #EF4423;
position: relative;
}

But nothing happened. Well not quite true, the background colour disappeared. But it did not centre.

Thanks for a grea theme!