When the Internet was booming, the SEO was a relatively new thing for the internet goers. it caught up when the early digital marketers realized the potential of internet search. It wasn't late until Google started investing in SERP Algorithm updates and Adsense/Adwords.
The history of SEO in a brief

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1990 - Internet opened to the public
1992 - Gopher became the first Search Engine / Wandex was introduced
1994-1996 - Site was built solely to market products / Amazon was founded
1995 - Yahoo was founded
1997 - Search Engine Watch was launched
1998 - Google Founded
2000 - Early concept of SEO began / Google Adwords was launched
2010 - Rise of Mobile Commerce
2010s - Google releases major Algorithm updates Later - Advent of Social Media
SEO Practices (In)
- Link and article directories
- Exact-match domains
- Reciprocal Linking
- Flat URL architecture
- Indiscriminate guest blogging
- Keyword stuffing
- Exact-match anchor text
- Pages for every keyword variation
SEO Practices (Out)
- Improve user experience
- Optimize for voice search
- Focus on topic instead of keywords.
- Post only relevant details
- Conquer video with YouTube SEO
- Build a variety of backlinks
- Get a grip over technical optimization
- Adopt Social networking