Why has google dropped indexing my website?

[CuriousGeorge]

We have a website at onlinepassportphoto.com. In last January (in 2012) we used to get around 500 visitors from Google Search but something went wrong and now we don't get more than 15 visitors from Google Search Engine. We are abiding to all of their rules and guidelines but not sure why Google is punishing us. Any clues or tips will be greatly appreciated.
Thanks Rahul and Jake.
* The drop in traffic is gradual- not sudden.
* I have Google Webmaster account. No warnings or no major errors. In the Index Status section, it says 228 files submitted but only 1 indexed!!!
* How can I see too many links from beststocktradingbook.com? I did a search on beststocktradingbook.com website but found links from only one page. I will keep looking for this and remove them.
Thanks