http:// and https:// I was talking to a couple of website self called Gurus and they said google downgrade sites rankings when not using the https:// any more. My bet this has been discussed here before. But one of my long time employees just pass and I have to hit the ground running and get back into this.
Google are certainly pushing sites to switch to https although there seems little signs of anyone being "downgraded" from what I've read. It is a good idea though and we have a long thread about it here you might want to read through https://www.ecommercetemplates.com/support/topic.asp?TOPIC_ID=106851