Trying to center a menu within a header?

Question

Here's a jsFiddle.

My goal is to have a menu with 95% width of the header centered.

Why doesn't the background color of the #header or the #menu show up?

When I do manage to have the background colors appear, it's not centered within the header.

Here's my code:

HTML:

<header id="header">    
      <nav id="menu">
        <ul id="nav">
            <li><a href="#">Home</a></li>
                <li><a href="#">Services</a></li>
                <li><a href="#">Contact Us</a></li> 
            </ul>
        </nav>
</header>

CSS:

#header {
    background: black;
}
#menu {
    background: #bf4040;
    position: relative;
    width: 95%;
    margin: 0 auto;
}
ul#nav {
    margin: 0;
    padding: 0 20px;
    width: auto;
}
    ul#nav li {
        float: left;
        padding: 0;
        list-style: none;
        list-style-image: none;
        margin: 2px 2px;
    }
    ul#nav li a {
        font-size: 12px;
        font-weight: bold;
        text-decoration: none;
        line-height: 37px;
        display: block;
        text-align: left;
        padding: 0px 15px;
        white-space: nowrap;
        text-transform: uppercase;
        color: #000;
        border-radius: 10px;
        -webkit-border-radius: 10px;
        -moz-border-radius: 10px;
    }
ul#nav li.current a, ul#nav li a:hover {
        color: #ffe200;
        background: #3d5a81;
    }

Answer 1

It's because they have no height! This is due to all the float: you are using, try replacing that with display:inline-block and you should be close to a solution.

http://jsfiddle.net/px4Qy/2/

I added text-align:right; to position the nav. Change this to text-align:center; to center the menu.

Answer 2

The #menu element isn't getting a background colour as it has no computed height since the nav items are floating, either set a fixed height on it or add overflow: hidden

#menu {
    background: #bf4040;
    position: relative;
    width: 95%;
    margin: 0 auto;
    overflow:hidden /* clears the floating elements giving the container height */
}