Running OnClick To Change Href Class CSS Style

I am using this javascript code to run 'onclick' to change my href class style. It works to change the style, but when I click on the next menu item, the previous one is not reverted back to how it was previously, but the formatting is stripped away leaving the link purple with no background image. How do I get it to revert to the original class which is set?

Here is the javascript :-
<script language="JavaScript" type="text/javascript">
/*<![CDATA[*/
var Lst;
function CngClass(obj){
if (Lst) Lst.className='';
obj.className='menu1';
Lst=obj;
}
/*]]>*/
</script>

Here is the relevant CSS :-
.menu {
background: url('../images/productblack.jpg') repeat;
width: 100%;
line-height: 24px;
float:left;
display:inline;
font-family: Verdana;
color : #ffffff;
font-size: 8pt;
text-decoration: none;
text-align: left;
font-weight:bold;
} .....

Here is the HTML :-
<div id="masterdiv">
<div onclick="SwitchMenu('sub1')"><a class="menu" onclick="CngClass(this);" href="javascript:nothing()"> 
RESISTORS</a></div>
<span class="submenu" id="sub1">
<a class="productsubmenu" href="resistors.html">Surface Mount</a><br> .....
Here is a working page with it (the product menu on the right) [URL]