net::ERR_INSECURE_RESPONSE with CDN
<p>I have deployed an app on heroku but the css is not working.</p>

<p>I am using the w3.css framework and I am importing it like this:
<code>&lt;link rel="stylesheet" href="//www.w3schools.com/lib/w3.css"&gt;</code></p>

<p>The error I am getting is:
<code>GET https://www.w3schools.com/lib/w3.css net::ERR_INSECURE_RESPONSE</code></p>

<p>I am pretty sure that it is related to the certificate of the site.</p>

<p>But even when I manually accept the "invalid" certificate in the site, I get a 404 error.</p>

<p>Also, from what I see, w3.css only offers its CDN through http:
<code>http://www.w3schools.com/lib/w3.css</code>
not https:
<code>www.w3schools.com/lib/w3.css</code></p>

<p>So, I just wanted to confirm that this is actually the case and that it is not my fault (not knowing how to load sth over https!)</p>

<p>Finally, it's not a Chrome error (from what I've read around in SO).
Firefox doesn't work either.</p>

<h2>UPDATE</h2>

<p>Just to inform that, as expected, the error was resolved when I downloaded the w3css framework and linked to it locally.</p>