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Changing a javascript variable through onclick on an anchor tag?

I have created this code but I cannot figure out why it is not working here is my code:

<!DOCTYPE html>
<html>
<head>
 <meta charset="UTF-8" />
 <title>jQTouch &beta;t</title>
  <style type="text/css" media="screen">@import "jqtouch/jqtouch.css";</style>
  <style type="text/css" media="screen">@import "themes/artspot/theme.css";</style>
  <style type="text/css" media="screen">@import "extensions/jqt.listIndex/jqt.listIndex.css";</style>
  <script src="jqtouch/jquery-1.4.2.js" type="text/javascript" charset="utf-8"></script>
  <script src="jqtouch/jqtouch.js" type="application/x-javascript" charset="utf-8"></script>
  <script src="extensions/jqt.autotitles.js" type="application/x-javascript" charset="utf-8"></script>
  <script src="extensions/jqt.bars/jqt.bars.js" type="application/x-javascript" charset="utf-8"></script>
  <script src="extensions/jqt.listIndex/jqt.listIndex.js" type="application/x-javascript" charset="utf-8"></script>
  <script src="jquery.tweet.js" charset="utf-8"></script>
  <script src="tweetstars.js" charset="utf-8"></script>


</head>

<body>
 <div id="jqt">
  <!--Homepage-->
  <div id="home" class="current">
   <div class="toolbar">
    <h1>Tweetstars</h1>
   </div>
   <ul class="rounded">
    <li class="arrow"><a href="#biglist">StarList</a></li>
   </ul>
  </div>
  <!--List of stars and popular people that publish tweets-->
  <div id="biglist">
   <div class="toolbar">
    <h1></h1>
    <a href="#" class="back"></a>
   </div>
   <div class="s-scrollwrapper">
    <div>
     <ul id="thelist" class="edgetoedge">
      <li class="sep">#</li>
       <li><a href="#">3 Ring Wing Ding</a></li>
       <li><a href="#">14 Carrot Rabbit</a></li>
       <li><a href="#">90 Day Wondering</a></li>
      <li class="sep">A</li><br/>
      <li class="sep">B</li><br/>
      <li class="sep">C</li><br/>
      <li class="sep">D</li><br/>
      <li class="sep">E</li><br/>
      <li class="sep">F</li><br/>
      <li class="sep">G</li><br/>
      <li class="sep">H</li><br/>
      <li class="sep">I</li><br/>
      <li class="sep">J</li><br/>
      <li class="sep">K</li><br/>
      <li class="sep">L</li><br/>
      <li class="sep">M</li>
      <li><a href="#tweetsof" onclick="usernamevalue = 'MarkFAngelo'">mairiboo</a></li>//when I enter there it does not show the tweets of MarkFAngelo.Instead it does not show the tweets of anybody
      <li class="sep">N</li><br/>
      <li class="sep">O</li><br/>
      <li class="sep">P</li><br/>
      <li class="sep">Q</li><br/>
      <li class="sep">R</li><br/>
      <li class="sep">S</li><br/>
      <li class="sep">T</li><br/>
      <li class="sep">U</li><br/>
      <li class="sep" id="V">V</li><br/>
      <li class="sep">W</li><br/>
      <li class="sep">X</li><br/>
      <li class="sep">Y</li><br/>
      <li class="sep">Z</li><br/>
     </ul>
    </div>
   </div>
  </div>
  <!--Artists and generally popular people-->
  <div id="tweetsof">
   <div class="toolbar">
    <h1></h1>
    <a href="#" class="back"></a>
   </div>
   <div class="s-scrollwrapper">
<ul class="rounded">
<li>
<script type="text/Javascript">
$(function(){
$(".tweet").tweet({
username: usernamevalue,
avatar_size: 50,
count: 20,
loading_text: "loading tweets..."
}).bind("loaded",function(){$(this).find("a").attr("target","_blank");});
});
</script>
<div class='tweet query'></div>
</li>
</ul>
</div>
</div>

</div>
</body>
</html>