A: 

Your question is not very clear...

The following code works... Maybe this helps?

<html>
<head>
<script type="text/javascript" src="http://jqueryjs.googlecode.com/files/jquery-1.3.2.min.js"&gt;&lt;/script&gt;
<style type="text/css">
    #tabMenu li        {display:block;float:left;background-color:green;}
    #tabMenu li a      {color:white;}
    #tabMenu li.active {background-color:blue;}
</style>
<script type="text/javascript">
    $(document).ready(function() {
        $('#tabMenu > li').click(function() {
            if (!$(this).hasClass('active')) {
                $('#tabMenu > li').removeClass('active');
                $(this).addClass('active');
            }
        });    
    });
</script>
</head>
<body>
    <div id="menu">
        <ul id="tabMenu">
            <li><a href="#">MenuItem</a></li>
            <li><a href="#">MenuItem</a></li>
            <li><a href="#">MenuItem</a></li>
        </ul>
    </div>
</body>
</html>
Ropstah