CSS--------------

ul#nav { list-style: none; position: relative; top: 53px; left: 0; margin: 0; padding: 0; }
ul#nav li { text-indent: -10000px; float: left; padding: 0; margin: 0; }
ul#nav li a { display: block; }

ul#nav #home, ul#nav #home a { background: url(/themes/template/images/nav/home.png) no-repeat; width: 50px; height: 30px; }
ul#nav #medjournal, ul#nav #medjournal a { background: url(/themes/template/images/nav/medjournal.png) no-repeat; width: 127px; height: 30px; }
ul#nav #medpress, ul#nav #medpress a { background: url(/themes/template/images/nav/medpress.png) no-repeat; width: 105px; height: 30px; }
ul#nav #case, ul#nav #case a { background: url(/themes/template/images/nav/casereport.png) no-repeat; width: 103px; height: 30px; }
ul#nav #questions, ul#nav #questions a { background: url(/themes/template/images/nav/p2p.png) no-repeat; width: 110px; height: 30px; }
ul#nav #userprofile, ul#nav #userprofile a { display:none; }

ul#nav #home a:hover, ul#nav #home a:active { background: url(/themes/template/images/nav/home.png) 0 -30px no-repeat; width: 50px; height: 30px; }
ul#nav #medjournal a:hover, ul#nav #medjournal a:active { background: url(/themes/template/images/nav/medjournal.png) 0 -30px no-repeat; width: 127px; height: 30px; }
ul#nav #medpress a:hover, ul#nav #medpress a:active { background: url(/themes/template/images/nav/medpress.png) 0 -30px no-repeat; width: 105px; height: 30px; }
ul#nav #case a:hover, ul#nav #case a:active { background: url(/themes/template/images/nav/casereport.png) 0 -30px no-repeat; width: 103px; height: 30px; }
ul#nav #questions a:hover, ul#nav #question a:active { background: url(/themes/template/images/nav/p2p.png) 0 -30px no-repeat; width: 110px; height: 30px; }


HTML

 <div id="header">
    <ul id="nav">
      <li id="home"><a href="/"><span>home</span></a></li>
      <li id="medjournal"><a href="/?q=medical-journal"><span>Medical Journal</span></a></li>
      <li id="medpress"><a href="/?q=medical-press"><span>Medical Press</span></a></li>
      <li id="case"><a href="/?q=case-reports"><span>Case Reports</span></a></li>
      <li id="questions"><a href="/?q=p2p-questions"><span>Peer Questions</span></a></li>
      <li id="userprofile"><a href="/?q=usernode"><span>Profile</span></a></li>
    </ul>
  </div>