title: how to center align a div containing floats without fixed width
body: <p>I have a ul menu inside a wrapper div. each li element has float:left (this is a horizontal menu).
  I want to center the menu in my page container (around 1100px), but I don't know what the size of the menu will be so I can't use "margin:0 auto".</p>
  
  <p>I tried many different things, but I just can't get this to work.</p>
  
  <p>This is a menu in wordpress, so the markup of ul and wrapper div is generated by wordpress. would prefer not to mess with that...</p>