Hi,
I am very much confused with the google. Suddenly the face google changes the site which is in ranking goes down . Why is it so. How can I target more visitors from google to my websites.
Please help me!!!!

its because Google are getting very strict in terms of checking the Quality of Backlinks and the Content of the Site. While writing post, be Original........

do quality keywords work

There has been a frequent changes in Google's algorithm that's why your sites ranking goes down. Just continue doing quality link building and have frequent updates on your site and your rankings will probably back to it's position.