You were penelized by google penguin. This is not good to hear. I have the same problem with one of my website. It was 2 mounth ago, now it is on 5 page. Continue with link building, but with quality one...

Here is one useful article which can help you

6 Ways To Find Out If You Are On The Google List Of Blacklisted Sites

Use Google Webmaster Tools to look at the site diagnostics - it will explain what happened, and suggest how to fix the problem

Maybe your site got hacked and when google try to crawl it doesn't see your site , happend to me few days ago and now im on page 2 out of 1 billion search for my keywords

Did you sign up webmaster tools for this website? This can have useful information about your website which have unnatural link detected or not.

first of all add your sitemap to google webmaster.

Once you have verify everything than send a request to Google and see whether they have manually done something or not.

If they say that they have not done anything than it is definitely Google Panda and Googe Penguin.

My suggest is if your website is not so important than move on new project and try to rank that website

I hope this helps.

In order to better diagnose what the problem was, you can check the date your website dropped, and after compare it to the dates of Google's algorithm updates. There were Panda updates and Penguin updates, and recovering from these is different.

Here are the latest dates:
Penguin - April 24, 2012
Panda 3.6 - April 27, 2012
Penguin 1.1 - May 25, 2012
Panda 3.7 - June 8, 2012

Is any of these close to the date your website dropped?

Be very carefull with the quality of your backlinks and the anchors you are using, you will find a lot of good articles about penguin update on the net.

Thanks guys,I'm waiting for more answers..

If it is the earlier stages of your online venture, then you are LUCKY.
If its your later stage then you need to go back to the drawing board again and rule out ALL free things from your business.

Thanks
Jay

My site completely disappeared from Google on May 20th but I was able to get it back in 25 days. I have written a blog post detailing the exact steps I did. You can read it at the link below.

What To Do If Your Website Disappeared From Google ? | Online Income Startup

Hope it helps...
Dr.Spencer Jones

Well, is your site registered in GWT...? If not insert it in GWT and check for if there is any notification from Google regarding whether or not your site is penguin penalized or not..

if your url still shows in google it didn't totally disappears. this happened to my money which disappeared most of the keywords. it happened during april. it was ranking on no. 4, from april till last week the traffic was very bad, but patiently i came back bit by bit. for now i haven't check where my main keyword is ranking now but i'm happy that my traffic is getting better.

Continue creating good quality backlinks and also concentrate on the quality of content. For getting back you have to create good quality backlinks with such pages which have good PR, not full with spam backlinks and definitely have to be in same niche. Best of luck.

Its becuase of google penguin update

Some of the advice in this thread is absolutely brillant! Thanks very much.