Basically if there is any insecure items on your SSL page.

Like -

• Insecure calls to images,css, and javascript
• Images called insecurely from linked css and js files
• Expired cert, invalid or missing intermediate certificate (including 3rd party SSL certs.)
• SHA-1 algorithm test, POODLE test, insecure form calls for Chrome

You can simply check if your web page is secured or not from here -

https://www.whynopadlock.com/