Thread: Traffic from google decreased !!!

my 80% traffic from google has dropped from last 3 days on grotal.com, i have 1.5 million pages indexed with google. pages are still indexed but traffic is zero
What is my Site about:
my site contains address, contact numbers and operational areas of business (products they deal with)
if i m looking for doctors in any city, my site lists all doctors in that city like this
grotal.com/Delhi/Doctors-C44/
now click on any result (title) or website
My Recent changes: i have opened an individual entry on a subdomain, means, i have created a website for every business man, these subdomains are made at run time, they are more than 500,000 in count,
google indexed these subdomains also, but after 5 to 6 days, my results start disappearing from google,
then i made some changes, i deleted anchar link from my domain to subdomain and put a javascript link, i put Noindex, Nofollow tag on these subdomain pages, i disallowed all bots in robots.txt for craweling these subdomains.
have i done good ? why google stopped showing my result? what is my fault, how can i resolve ?
please help me, your help will be appreciated.

You must check your Google analytics report to pin point the keywords for which traffic is being falling down.
Also, look out for pages which are facing downfall in traffic and try to improve them.