I have a #header div that is 100% width and within that div I have an unordered list. I have applied 'margin: 0 auto' to the unordered list but it won't center it within the header div.
Can anybody please tell me why? I thought that if I define the width of the parent div, then the unordered list should be able to center itself with margin: 0 auto. What am I missing?
Here is my code:
<style>
* {
    margin: 0;
    padding: 0;
}
#header {
    width: 100%; 
    background-color: #333;
    min-height: 160px;
    font-family:Arial, Helvetica, sans-serif;
}
#sitename {
    font-size: 50px;
    width: 620px;
    margin:0 auto;
    padding-top: 35px;
    color:#999;
}
#header ul {
    float: right;
    margin: 0 auto;
}
#header ul li {
    float: left;
    padding-right: 20px;
    list-style-type: none;
    font-size: 20px;
}
</style>
</head>
<body>
<div id="header">
    <h1 id="sitename">Photography Auction Site</h1>
    <ul>
        <li>List of Photos</li>
        <li>Image Gallery</li>
        <li>Contact Us</li>
    </ul>
</div>
</body>
</html>