iframe自适应的代码

<script language="javascript">
   function iframeAutoFit()
   {
      try
      {
         if(window!=parent) { var a = parent.document.getElementsByTagName('IFRAME');
            for(var i=0; i<a.length; i++) //author:meizz
            {
               if(a[i].contentWindow==window)
               {
                   var h = document.body.scrollHeight;
                   if(document.all) {h += 4;}
                   if(window.opera) {h += 1;}
                   a[i].style.height = h;
               }
            }
         }
      }
      catch (ex)
      {
         alert('脚本无法跨域操作！');
      }
   }
   if(document.attachEvent)  window.attachEvent('onload',  iframeAutoFit); 
   else  window.addEventListener('load',  iframeAutoFit,  false); 
        </script>