After EdgeSSL is live, mixed content is almost always leftover http:// in HTML.
Fix list
- Search origin for
http://cdn.andhttp://*.netdna-cdn.com. - WordPress: W3TC CDN → HTTPS, then empty caches. Guide: W3TC.
- Magento: update Base Skin/Media/JS URLs to https. Recipe: Magento 1 / Magento 2.
- Purge the zone.
- Open DevTools → Console. Mixed-content warnings should be gone.
Protocol-relative //cdn.example.com only if you still have HTTP and HTTPS HTML. Prefer https.
The Science of Acceleration