1. Not having a mobile-friendly website
2. Not having unique and quality content
3. Not using the right keywords
4. Not using any keywords at all
5. Not using social media
6. Not using Google Analytics
7. Not using Google Webmaster Tools
8. Not optimizing your website’s load time
9. Not having a sitemap
10. Not linking to other websites 11. Not using H1 or H2 tags
12. Not using alt tags
13. Not using title tags
14. Not using meta descriptions
15. Not using internal linking
16. Not using external linking
17. Not using anchor text
18. Not using robots.txt file
19. Not using a .htaccess file
20. Not redirecting your 404 error pages