Search Engine Penalties

Sometimes Google search listings will simply lose a website. It may cause fall of website from search results, or sometimes websites are disappear from search results too.The search engines are computer programs. They are not perfect all time. Sometimes a website will merely fall through the virtual cracks. After a couple of weeks to a month, the spiders will have crawled the website a few more times. Following a reindexing, the site will once again be included in the Google search results.
The best method to getting a website back in Google's good graces is to adhere completely to Google's guidelines, and then wait. The process will be a slow and frustrating one, so patience is strongly recommended.

Mainly we can categorised penalties into two main types
Perceived and Actual penalties
1. Perceived search engine penalties: Sometimes people assume that their site has been penalized if the site experiences a lost in ranking in search engines. However, many of these perceived penalties are in fact a reflection of other changes or issues that may be taking place with the search engines or even within a webmaster's own site.

Other perceived penalties include:

1. Server is down or having problems during crawl, so pages aren't indexed
2. Robots.txt could be badly written
3. Problems with crawlers
4. Virtual crawling problems
5. Domain name problems
6. Lost links causes ranking to drop
7. Rankings drop because other sites are better or have more links
8. Rankings drop due to a search engine algorithm shift

At this time you have to Spend some time analyzing your search engine result pages (SERPs). Most of Google's penalties are automatic, and once you remove the offending factors, the penalties will be automatically lifted. You may have to wait at least a month, but at least the penalties will be removed. To speed up the process, you can also search for high quality, trusted websites to link to your site. This will give your site Trust Rank points and help your site recover quicker and more effectively.

Check Wheather your site is Penalise or not

Do ""www.abc.com"" ( Use Quote 2 times )
I believe that if your site does not come up first you are under penalty. We are coming on top so most probably we are not penalized.

When a penalty is suspected, start by checking with Google the number of URL's it has indexed. This can be accomplished by using the site:www.abc.com -asdfdfdgdf command within a Google search window. If no URL's are indexed and no backlinks show up when the link:yourdomain.com is entered then there is a high probability of a Google penalty, especially if your site /used to be indexed/ and /used to show backlinks.

Reciprocal link building campaigns - may also trigger a Google penalty or cause a SERPS filter to be applied when the same or very similar link anchor text is used over and over again and large numbers of reciprocal links are added in a relatively short time. The dangers are made worse by adding reciprocal links to low quality sites or websites which have an unrelated theme. This can lead to a backlink over optimisation
penalty (known as a BLOOP to SEO experts!).

To avoid this problem, reciprocal link exchange should only be used as part of a more sustainable SEO strategy which also builds quality one way links to original website content. Don't forget to check that prospective reciprocal link partners have a similar theme as your homepage using the _Google site flavored search
http://labs.google.com/personalized/siteflavored box.

Contact Google at help@google.com help@google.com> They will check the "spam report queue" to see if a Google spam report has been filed against your domain by a third party.