The influence of a site to attract the visitors is based on the quality of that site. The quality of a site can be measured through several factors one of them is ranking. There are different kinds of ranking systems are there which is based on several factors. Such 3 ranking systems are google pagerank, alexa rank, technorati rank. These are the top ranking medias in the seo.
1) Pagerank:- pagerank for a site is given by the google search engine it is based on the traffic that the site recieves, content update of the site etc. There is a concept that google loves content it is true that if a site has maximum content rather than pictures and media it is possible to get pagerank. Pagerank help a site to get listed in top search results.
2)Alexa:- Alexa rank is completely based on the traffic that the site recieves. They give a rank to a site by measuring compative skill of the site with other site to get traffic. Alexa checks a site for more than 3 month to give a rank. In order to get a rank the webmaster have to claim that site by inserting there code.
3)Technorati:- Another seo ranking system which give rank to a site based on the content updates of the site. This rank also help the site to link with different category on top board. This rank also help the site to value the quality of the content that it recieves.
So ranking is an important component in blogging as well as the value of the site. All the best.