Drop in Google Searh Results and in Traffic

Hi,
I have website of Pin code details of India.There is traffic of 300 visits daily.But, suddenly on 12th March there is drop in google ranking and also in traffic.
But i hadn't get any message on webmaster tool regarding the drop in ranking or traffic.
I cant understand why this happened as still there is no google algorithm update .Also i had not done any Black Hat SEO.Only some 50 to 60 Social
Bookmarking had been done for inner pages.
Please guide me.

See original post by adixit99