Highlight menu item onclicl

I have found several questions to this. I am trying to highlight a selected menu item.

The current code I am using is

<script src="JavaScript/jquery-1.10.2.js" type="text/javascript"></script>

<script>
function active_menu() {
    var url = window.location.href;
    $('.nav a').filter(function() {
        return this.href == url;
    }).addClass('current');
}
</script>
<!--Start Menu -->
  <ul id="nav">
      <li><a href="index.php">Home</a></li>
      <li><a href="runetable.php">Rune List</a></li>
      <li><a href="alpha.php">Runic Alphabet</a>
      <li><a href="trans.php">Runic Transliteration</a></li>
      <li><a href="aetts.php">The Aetts</a></li>
      <li><a href="runes.php">Runes</a>
          <ul>
          <li>Freya's Aett</li>
          <li><a href="fehu.php">Fehu</li>
          <li>Uruz</li>
          <li>Thurisaz</li>
          <li>Ansuz</li>
          <li>Raidho</li>
          <li>Kenaz</li>
          <li>Gebo</li>
          <li>Wunjo</li>
          <li>Hagal's Aett</li>
          <li>Hagalaz</li>
          <li>Nauthiz</li>
          <li>Isa</li>
          <li>Jera</li>
          <li>Eiwaz</li>
          <li>Perthro</li>
          <li><a href="algiz.php">Algiz</a></li>
          <li>Sowilo</li>
          <li>Tyr's Aett</li>
          <li>Tyr</li>
          <li>Berkana</li>
          <li>Ehwaz</li>
          <li>Mannaz</li>
          <li>Laguz</li>
          <li>Inguz</li>
          <li>Dagaz</li>
          <li>Othila</li>
          </ul>
        </li>
      <li><a href="about.php">About</a></li>
      <li><a href="contact.php">Contact</a></li>
  </ul>

<!-- End Menu -->

This code works… Sort of…
I have found maybe 5 or 6 examples and I have run into the same problem with all of them.

Items 2, 6, and 7 will not highlight. That would be Rune List, Runes, and About.

I do not understand why these entries will not highlight, no matter which solution I try. As I said, I have tried a few and they all work except for those menu items.

Can anyone point me in the right direction? I am going nucking futs trying to figure this out.

Thanks for reading!
Jim