My 90% Traffic decreased, i m ruined :(

[parvaiz13]

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.

[Hogward]

Do some keyword research and target the keywords which are capable for conversions. Its better to move up with long tail keywords.

Make use of social networks this helps to drive lot of traffic for your site.

[prcys]

There may be three major reason for decreasing traffic. As one is you have not enough information pr you get less backlinks to your site or your KW be not searched more. Ok but now try to get more traffic again and this time be careful and use blog , articles , and videos for more traffic with relevant KW and , you can do it with social media which is so effective.

[jargonbust]

search for reason why this happened and check if you have not been penalized by google