double centered in unknown or dynamic sizes

by kseso

HTML

<ul>
<li><a href="http://ksesocss.blogspot.com/">Inicio</a></li><li>
  <a href="http://ksesocss.blogspot.com/p/contacto.html">Contacto</a></li><li>
  <a href="http://feeds.feedburner.com/Ksesocss" rel="rss">Rss</a></li><li>
  <a href="http://twitter.com/kseso/">Twitter</a></li><li>
  <a href="http://ksesocss.blogspot.com/2012/11/netK.html">netK</a></li>
</ul>

CSS

@import url(http://fonts.googleapis.com/css?family=Tenor+Sans);
* {margin: 0; padding: 0; border: 0 none;}
html {background: #f9f9f9  url(http://2.bp.blogspot.com/-Gi0cA9n_aKw/T2Yki1S2RTI/AAAAAAAAAJs/Gvo3P_ts5Fw/s1600/reticula-2.gif) repeat center center;
}
ul {
  position: absolute;
  width: 100%;
  top: 50%;
  margin-top: -15px; /* 50% of the line-height in a */
  text-align: center;
}
li {
  display: inline-block;
  list-style: none;
  margin-left: 5px;
}
li:first-child { margin-left: 0;}
li a {  
  background: #5fa9c5; 
  border: 1px solid #777; 
  display: block;
  font-family: Tenor Sans, sans-serif;
  color: #444;
  font-weight: bold;
  text-decoration: none; 
  line-height: 30px; /*margin-top of ul plus 2*/
  padding: 0 10px;
  text-shadow: 1px 1px 0 rgba(255,255,255,0.1);
border-radius: 4px;}

a:hover {
  background: #363636;
  color: #5fa9c5;
  border: 1px solid #5fa9c5;
}
/* IE7 hack, if you need or want
li { *display: inline; zoom: 1; }
*/