No SSL padlock - HTTPS validation failed, mixed active content warning

If you have configured https website and see SSL validation error (no green padlock) you need to perform this actions:

• Make sure you have valid SSL certificate installed (ask hosting support for help with this)
• Make sure you have Force SSL or similar plugin installed
• Make sure you have all site urls starting with https:// in Settings > General.

If you see https error about some file from wp.com subdomain:

• Remove sample user imported with demo data or remove sample posts (this error comes from test user avatar loaded from WordPress via http).

If you see https error about logo image file:

• Go to Appearance > Theme settings > Logo and scroll down to see Logo for Transparent Header (Light logo) option. Upload your light logo version here (or remove sample logo loaded with demo data).