Particularly, don't embed CC0 button from unencrypted HTTP site.
newly-designed glyphs have been released into the public domain.</p>
<p>
<a rel="license"
- href="http://creativecommons.org/publicdomain/zero/1.0/">
- <img src="http://i.creativecommons.org/p/zero/1.0/88x31.png"
+ href="https://creativecommons.org/publicdomain/zero/1.0/">
+ <img src="https://i.creativecommons.org/p/zero/1.0/88x31.png"
style="border-style: none;" alt="CC0" />
</a>
</p>