set up your events using the methods they provide and it should work. try setting them up like this...
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<script>
function init() {
document.getElementById("spanID"

.addEventListener("mouseout", someFunction, true);
document.getElementById("spanID"

.addEventListener("mouseover", someFunction, true);
}
function someFunction() {
alert("hello world"

}
</script>
</head>
<body onload="init()">
<span id="spanID">this is a test</span>
</body>
</html>