"The isHomePage method will always return false if the document that is calling the isHomePage method is not on the same domain. For example, if www.microsoft.com is set as your homepage, and you call this method from a page on the Microsoft® Web site, then the isHomePage method returns true. However, if your homepage is set to www.microsoft.com and you call this method from a page on a different domain, the method will return false. "
assodato questo, se non provi online non potra' che ritornare falso

codice:
<!--[if gte IE 5.5]>
<span id=hp style="behavior:url(#default#homepage)"></span>
<script type="text/javascript">
var thePage='http://www.tuodominio.it/index.htm';
var theText='Imposta questa pagina come homepage!';
if (!hp.isHomePage(thePage)) {document.write("

"+theText+"");}
</script>
<![endif]-->
ciao