In the days of Alta Vista, Yahoo, and other similar search engines that existed long before Google came into existence, content was the sole factor that was primarily used for ranking sites. Word-length and uniqueness of articles were the particularly-observed signals among the other ranking factors.

With effect from 1998, the ranking system changed totally when Google took over the ranking of sites and developed its own search algorithms. Several factors were considered by Google which made the ranking system much more accurate than it used to be when it was still managed by Alta Vista, Yahoo and other similar search engines.

Google looked into content and built the ranking algorithm based on the following top factors:

• Content quality
  
• Topic relevance
• Content readability
• Content length
• Link quality
• Visitor engagement
  
• publishing frequency; and
• Image relevance.

Content Quality

Google does not read through the words in all of your content though, it checks to see if your content is informative, compelling, engaging, remarkable and helpful.

It checks your keyword quality, use of English grammar, punctuation marks such as question mark, full stop, commas, hyphen, apostrophe, colon, exclamation mark, and many others. All these amount to the quality of your content in the sight of Google.