What is wrong with this and how could I fix it. I have css menu (horizontal) that I want the background and font to be changed when one of the items is selected. I found another post that gave me some jquery code to help make it work, and I thought I had it coded right, but when I click on an item to change its class it adds the class, but the background and font stay the same? Any ideas here?

Heres the HTML

<ul id="menu_nav" class="buttons">
  <li>
    <a href="#" onclick="' . $menu_path . '">Item 1</a>
  </li>
  <li>
    <a href="#" onclick="' . $menu_path . '">Item 2</a>
  </li>
  <li>
    <a href="#" onclick="' . $menu_path . '">Item 3</a>
  </li>
</ul>

Heres the CSS:

ul#menu_nav
{
    float:left;
    width:790px;
    padding:0;
    margin:0;
    list-style-type:none;
    background-color:#000099;
}
ul#menu_nav a
{
    float:left;
    text-decoration:none;
    color:white;
    background-color:#000099;
    padding:0.2em 0.6em;
    border-right:1px solid #CCCCCC;

    font-family: Tahoma;
    font-size: 11px;
    font-style: normal;
    font-weight: bold;
    position: relative;
    height: 21px;
    line-height:1.85em;
}
ul#menu_nav a:hover {
    background-color:#F1F4FE;
    color:#000099;
    border-top:1px solid #CCCCCC;
}
ul#menu_nav li {display:inline;}

.selected {
    background-color:#F1F4FE;
    color:#000099;
    border-top:1px solid #CCCCCC;
}

Here's the Jquery:

$(function(){
  $(".buttons li>a").click(function(){
    $(this).parent().addClass('selected'). // <li>
      siblings().removeClass('selected');
  });
});