Just a few days back my site ranked at 1st place in msn for the terms "pertusis disease". Now it is nowhere to be seen. I made some changes to the site by including 17 new sub-domains. Can this be a reason? Should I remove the sub-domains? Also how do I change the site from http://xyzxyz.com to http://www.xyzxyz.com?
Thank you in advance for your advice.