http://www.mymobnet.com/alexa-accepts-faults-in-their-site-ranking-system/
Alexa website ranking is no doubt the most popular internet ranking site online. Alexa web ranking also may be the most trusted site ranking company also.

But often and on site owners have complained and written a lot on the inadequacy of Alexa site ranking system. Sites are ranked by it mainly due to traffic and number of quality link in from other websites.

Any, Alexa, the Amazon owned company have admitted of this error in site ranking and promise to improve drastically as soon as possible in providing better ranking service. According to the notification from Alexa.com:
http://www.mymobnet.com/alexa-accepts-faults-in-their-site-ranking-system/