title: Google Plus Sign-In button rendered but not working
body: <p>I'm trying to get comfortable with the Google APIs. </p>
  
  <p>To study the sign-in process, I built a simple web page to get the sign-in button working according to <a href="https://developers.google.com/+/web/signin/add-button" rel="nofollow">https://developers.google.com/+/web/signin/add-button</a> and the button is rendered properly. However, it is not active - it doesn't react to clicks, there's also no error in the browser console.</p>
  
  <p>I do not run the page from a web server, I'm opening it directly from disk. I.e. the URL is something like <code>file:///c:/projects/GooglePlusClientJS/google_plus_js.html</code>.</p>
  
  <p>The page code:</p>
  
  <pre><code>&lt;!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"&gt;
  &lt;html&gt;
    &lt;head&gt;
    &lt;meta http-equiv="content-type" content="text/html; charset=utf-8"&gt;
  
    &lt;script src="https://apis.google.com/js/client:platform.js" async defer&gt;&lt;/script&gt;
    &lt;script type="text/javascript"&gt;
  function signinCallback(authResult) {
    if (authResult['status']['signed_in']) {
      // Update the app to reflect a signed in user
      // Hide the sign-in button now that the user is authorized, for example:
      console.log("Signed in");
      document.getElementById('signinButton').setAttribute('style', 'display: none');
    } else {
      // Update the app to reflect a signed out user
      // Possible error values:
      //   "user_signed_out" - User is signed-out
      //   "access_denied" - User denied access to your app
      //   "immediate_failed" - Could not automatically log in the user
      console.log('Sign-in state: ' + authResult['error']);
    }
  }
    &lt;/script&gt;
    &lt;title&gt;GooglePlus Test&lt;/title&gt;
    &lt;/head&gt;
    &lt;body&gt;
  
  &lt;span id="signinButton"&gt;
    &lt;span
      class="g-signin"
      data-callback="signinCallback"
      data-clientid="my_client_id.apps.googleusercontent.com"
      data-cookiepolicy="none"
      data-requestvisibleactions="http://schema.org/AddAction"
      data-scope="https://www.googleapis.com/auth/plus.login"&gt;
    &lt;/span&gt;
  &lt;/span&gt;
  
    &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>What am I doing wrong? Is it caused by opening it directly from disk? If so, why?</p>
  
  <p>Thanks.</p>
  
  <p>EDIT 1: When running off of a web server, the page seems to work fine, the logon dialog is being displayed. Can anyone shed a light on why this happens?</p>