I said 'dumb' because I feel like I should know this with all the experience I've had with HTML5... i'm probably just missing something really stupid... but here's the code, I've having trouble centering the <ul>:

CSS:
#nav {background-color: #804000; float: left; padding: 5px; margin:2px;}

HTML:
<ul style="list-style:none;" align="center">
<li id="nav" onclick="hide('ma')">MIDDLE AGES</li>
<li id="nav" onclick="hide('rn')">RENNAISSANCE</li>
<li id="nav" onclick="hide('bb')">BAROQUE</li>
<li id="nav" onclick="hide('cc')">CLASSICAL</li>
<li id="nav" onclick="hide('rr')">ROMANTIC</li>
<li id="nav" onclick="hide('me')">MODERN EUROPE</li>
<li id="nav" onclick="hide('mna')">MODERN NORTH AMERICA</li></ul>

I've also tried other things, like <center>, style="text-align: center;" and more