How to give a different color to a selected list item with CSS?

Question

I know this question has been asked so many times before. But I just can't find the right trick for my code. I want a different color for my active list item in the navigation bar. Obviously. Silly little thing. I know. But please try to help.

Here's my HTML code:

<div id="container">  
    <ul id="nav">  
        <li class="active"><a href="am_home.html">Home</a></li>  
        <li><a href="am_teachingassistants.php">Teaching Assistants</a></li>  
        <li><a href="am_courseinfo.php">Course Info</a></li>  
        <li><a href="am_timetable.php">Time Table</a></li>  
    </ul>  
</div>  

and Here's the CSS file:

#container {
    position: relative;
    top: -2em;
    z-index: 2;
    width: 1200px;
    margin: auto auto;
}

#nav {
   position: relative;
   float: left;
   margin-left: 400px;
}

#nav li {
    list-style: none;
    float: left;
    border-right: 1px solid #afc4cc;
}

#nav li a {
   position: relative;
   z-index: 2;
   float: left;
   padding: 5px 45px;
   font-size: 15px;
   font-weight: bold;
   font-family: helvetica, arial, sans-serif;
   text-decoration: none;
   color: #39aea8;
}

ul, li {
    margin: 0;
    padding: 0;
}

ul#nav li a:link,ul#nav li a:visited {
    color: #39aea8;
    text-decoration: none;
}

ul#nav li a:hover,ul#nav li a:active {
    color: #f4ba51;
    text-decoration: none;
}

Answer 1

There's something wrong with your CSS code. Just replace this:

 ul#nav li a:hover,ul#nav li a:active{    
}

with this:

 ul#nav li a:hover,ul#nav li.active a{
 // here styling 
}

and you are good to go. You just made a mistake while calling the active class in CSS.