SEO is basically this includes both on-page and off-page optimization. As all search engine has their own system for search and selecting websites called algorithm to decide the web sites that meet best to their criteria and therefore have the higher SERP natural listing positions or ranks for a given keyword or keyword phrase in a user search query.
Apart from On page SEO there are many factors that measured by the major search engines for evaluating the off-page optimization of your web site and that include:
Relevancy : What kind of web sites are linked to your web site? Most of search engine work on this method that the web sites linked to your site are relevant to the content of your web site and the linking site is considered an authority in its field by the search engine.
How many web sites are linking to your site? The number of relevant sites that link to you is a significant plus for your site.
PAGE RANK: Google has a policy of PAGE RANK and so Google page rank (1-10) of each web site that links to your site is also Important. More the page rank more better is the rank. This is a major factor for google and a high page rank relevant site linking to your site is much better than a low page rank site with more non relevant links. A site’s ranking power increases as the page rank of the site increases.
What is the anchor text of each link to your site? The anchor text indicates the area of relevance the linking site places on your site. This anchor text should include your primary keywords. The text in the linking anchor text should not be the same in every site linking to your site. This is not seen as natural linking by the search engines. You need to get variability in the anchor text.
What is the page title of the web page that is linking to your site? It is better if the title page of the linking web page is relevant to your site and contains one of your keywords in its title. If it just says “link directory” then that is not good.
Is the link to your site a reciprocal link or a one-way link? A reciprocal link means you have linked back to the web site that linked to you. This can be a negative to your site because you lose some of your site’s page rank to the other site. If you do resort to reciprocal links, make certain the page rank of the other site is the same or higher that the page rank of your linking page. The one- way link to your site is a much better deal because you do not lose any of your site’s page rank.
If you want to achieve high natural page listing on the search engines, you need to evaluate and utilize some of the factors in both on-page and off-page optimization.