iframe failed load in ie6

at the day i include to my web page an iframe , in browser like firefox , opera works fine, but in ie6 sometimes cannot load the content of iframe , and a code who load page in iframe

<iframe frameborder="0" scrolling="no" src='index.php' name='mainFrame' onload='in_process = false;
resizeIframe("mainFrame");'
id='mainFrame' width="100%">
</iframe>


the follow show IE6
http://www.artwork.com/support/windows/download2.gif

We'd need to be able to see the website live, or at least more code, to determine what the problem is.