Checking user's homepage in Internet Explorer

Question

Google displays a popup that asks if you want to set your home page as google.com. It's quite normal, when I say OK it sets it as google.com. After that however, I don't get the popup anymore. As far as I know, nobody should be able to retrieve the value of my homepage because it's a private info. But somehow Google is tracking it. I get the popup back when I set my homepage as a different site. I deleted the cookies but even then it is only displayed when I set homepage as another site.

I tested this behavior on IE8 & IE9. The popup never shows up in Firefox and Chrome.

Answer 1

Internet Explorer makes it possible to ask it whether a given URL is the home page, it's detailed on this MSDN page. That links to this example page demonstrating the API.

Answer 2

The code Google uses can be viewed here:

google.promos.mgmhp.isGoogleHomepage = function (a) {     var b = !1;     try {         b = window.external.isGoogleHomePage()     } catch (d) {         if (h(a)) return !0;         var c = google.promos.gpd(a, "mgmhp_hp_url");         c && g.push(c);         for (c = 0; c < g.length; c++) {             var k = g[c];             if (b = b || a.isHomePage(k)) return !0         }     }     return b }; 

They are using the proprietary isHomePage method to check if google.com is your homepage. More info here.