使用object.filters.alpha.opacity报错该怎么办？

贴代码:
function high(which2){
  theobject=which2;
  highlighting=setInterval("highlightit(theobject)",50);
}function low(which2){
  clearInterval(highlighting);
  which2.filters.alpha.opacity=60;
}function highlightit(cur2){
  if (cur2.filters.alpha.opacity<100){
    cur2.filters.alpha.opacity+=5
  }else{
    if (window.highlighting)
    clearInterval(highlighting)
  }
}
<body>
<td>
  <img src="/Images/INDEX_top_05.jpg" class="PicAlpha"  onmouseover=high(this) onmouseout=low(this)>
</td>悬而未决