求求各位看看吧，firefox对JavaScript的问题

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html>
<head> 
<title> </title> 
</head> 
<body> 
<a href="javascript:void(0);"> <span id="s1" style="color:#0000FF" onclick="test(this)">111 </span> </a> 
<a href="javascript:void(0);"> <span id="s2" style="color:#0000FF" onclick="test(this)">222 </span> </a> 
<a href="javascript:void(0);"> <span id="s3" style="color:#0000FF" onclick="test(this)">333 </span> </a> 
<script language="javascript">
function test(obj){ 
document.getElementById("s1").style.color="#0000FF"; 
document.getElementById("s2").style.color="#0000ff"; 
document.getElementById("s3").style.color="#0000ff"; 
obj.style.color="#ff0000";
} 
</script> 
</body> 
</html>