Google uses a sophisticated and proprietary algorithm for ranking Web sites that uses over 100 different criteria in the calculation, each of which is given a specific weighting which can change over time. Because the algorithm can change, specific techniques that used to work well may no longer work as well over time. This is important to remember when your site’s ranking seems to change for no apparent reason. For this reason, optimizing your site should not be considered as a one-time task. You should always try, test, and refine your efforts.
Thats why we say.Keep updating your website