Changing Span Class not working

Changing Span Class not working

I have the following code in a webpage and for some reason unbeknown to me
it is not working, I have 2 methods to try to change the spans class
attribute but it is not working, can someone please point be towards where
I have gone wrong? :)
<script language="javascript">
function ChangeClass()
{
alert("Clicked!");
document.getElementById("Search").className = "SC-non-activeTab";
alert("Changed class!");
//does not work
}
window.onload = function()
{
document.getElementById("Search").addEventListener('click' ,
ChangeClass );
var elm = document.getElementById("Search").className;
alert("LOADED PAGE " + elm);
//this works
}
function someFunction(abc,elm) {
alert(abc + "/" + elm);
//does not work
}
</script>
<div class="tabs" id="tabs">
<div class="tabOutline" id="outline" >
<span class="activeTab" id="Search"
onclick="someFunction('two',this.className)">
Search
</span>
</div>
</div>