You wanted to access the root document of server www.google.com, which is done using the url https://www.google.com/. You provided a relative url for document www.google.com instead.
Keep in mind that window.open accepts both relative and absolute urls, so it can’t assume you left out https:// as it does when you use www.google.com in the address bar.
Maybe an example will help. Say the current page is http://www.example.com/dir/foo.html.
window.open("popup.html", "_blank")openshttp://www.example.com/dir/popup.html.window.open("www.google.com", "_blank")therefore openshttp://www.example.com/dir/www.google.com.
The browser has no way of knowing you actually wanted https://www.google.com/ when you said you wanted http://www.example.com/dir/www.google.com since the latter could be valid.