le hice unas cuantas modificaciones
Código:
<html>
<head>
<!-- Copiar dentro del tag HEAD -->
<style type="text/css">
#im {
FILTER: alpha(opacity=100)
}
</style>
<script language="JavaScript1.2">
function high(which2)
{
theobject=which2;
highlighting=setInterval("highlightit(theobject)",50);
}
function low(which2)
{
clearInterval(highlighting);
which2.filters.alpha.opacity=100;
}
function highlightit(cur2)
{
if((cur2.filters.alpha.opacity==100)||((cur2.filters.alpha.opacity<100) &&(cur2.filters.alpha.opacity>50)))
cur2.filters.alpha.opacity-=5
else if(window.highlighting)
clearInterval(highlighting)
}
</script>
</head>
<body>
<img SRC="logo_header.gif" id="im" onmouseover="high(this)" onmouseout="low(this)">
</body>
</html>