Google indexes and scores a web page for keyword relevancy. The relevancy of a site's web page content for keywords / key phrases requires site optimization or on-page optimization. Google factors a web page's content based on keyword relevancy, keyword density, and keyword proximity.
Here are some of Google's ranking factors:
1. Relevancy of Title text
2. Relevancy of Meta Description text
3. Relevancy of Body text
4. Relevancy of HTML tag "IMG" Alt text
5. Relevancy of HTML comments
6. Proximity of keywords to top of page
7. Page loading time
8. Density of keywords
9. Number of outbound links
10. In-linking between pages
These are just some of the requirements for on-page optimization of web pages. Google has more than a hundred of ranking factors and some of these factors are secrets that only the Google Engineers know about.
