Why do websites say not secure?

Related questions

1. Should I use Safari?
2. Why is my website insecure?
3. Can you uninstall Safari?
4. Why is my connection not private?
5. How do I see extensions in Safari?
6. Where is the extensions button on safari?
7. How do I get rid of Safari extensions on my iPhone?
8. Is Chrome faster than Safari on iPhone?
9. What is the best Adblocker for Safari?
10. What are extensions for Safari?

Tags

1. #chrome
2. #seeing
3. #connects
4. #visiting
5. #because
6. #browser
7. #providing
8. #connection
9. #either
10. #cause
11. #insecure
12. #website
13. #reason
14. #https
15. #secure
16. #warning