Some sites, like Google, have "frame busting" code on their pages to prevent them from being hosted in an iframe, which is why you see the behavior you do. Other sites, like palermo4.com, do not have such code and thus work fine.
In Windows 8 there is no workaround for this, unfortunately. In Windows 8.1 Preview you can use the x-ms-webview element instead (See the
Webview sample for HTML/JS), which can host sites like Google. This is one of the main scenarios that drove the webview API for 8.1. I also discuss it in the my book's
second edition preview (Chapter 4)
Kraig
Author,
Programming Windows 8 Apps with HTML, CSS, and JavaScript,
a free ebook from Microsoft Press