I have a sharepoint hosted app page. 

I have a link in it. Clicking on it it should open a modal pop up whose url is the home page of the sharepoint site. 

I am able to open a modal pop up window but it is not showing any content of any external site. I tried the url as "<http://www.google.com/>", still the modal pop up window was blank. 
I have used the code :

```
<script type="text/javascript" >
    function openDialog(strPageURL) 
      {
        var options = {
            url: strPageURL,
            showMaximized: true,
            width: 800,
            height: 500,
            title: "Title of Dialog"
        };
        SP.SOD.execute('sp.ui.dialog.js', 'SP.UI.ModalDialog.showModalDialog', options);
        SP.UI.ModalDialog.showModalDialog(options);
    }
</script>

 <a onclick='javascript:openDialog("http://www.google.com");javascript:return false;' href="#" target=_self> Click to Open</a>

```

Any idea why the content of the modal is null or displaying null?