Google is changing its algorithms frequently just do what you are doing and focus on keywords that are small key phrases as of instant search.
seeing the same effect on some of my sites. for the same domain name, some keyword ranking fluctuated, while some keywords remain. also, some competitor site with poor strength/backlink/content get ranked top, which i doubt there is some problem with the search engines lately. watching and tracking right now, learn from seo expert in this forum does help too, don't give up.
The algorithms are a closely guarded secret, and they are always changing, if they released the algorithm, then everybody would overload their servers, spammers et al, and they would have to start from scratch finding a way to sort out the relevant sites from the junk
Can you provide us with the URL and keyword? It will be easy to check if there is any penalty issue or any other options that may have resulting this.
Yeah continue to work on the site and also a few other keywords.. It will shortly come back after some time depending on the niche.
Then try doing site:www.sitename.com. If you can see the pages in the index, then its ok..if not then you should analyze your site for spammy content.
There can be various reason behind it such as keyword, broken backlinks, error or heavier webpages. Other thing can be, if you are not updating your website on an regular basis, I mean 2 or 3 times a week, then you can slip badly in ranking. Google has introduced Caffeine system in their search engine, which gives high priority to fresh contents, if you will not update your site it will found your website less useful than others, hence loss in traffic as well as ranking.... so try it...
sometimes google out over sites to his search engine because we can do lots of spamming... don't worry about that.. just stop spamming and make unique post.. do some do-follow blogs, and make some back links.. in couple of days you site will be shows on google search engine .....
Keywords in URL, Keywords in <title> tag, Keywords in anchor text, Keyword density in document text, Keywords in headings (<H1>, <H2> tags), Keywords in <alt> tags, Keywords in the beginning of a document, Keyword phrases. These are positively affect your search engine rankings
It always happen so i strongly suggest that you just keep working on your site and wait because sooner or later google will put back your rankings
Google is also changing its search strategy as instant search is just come in so it will also create huge impact on keywords ranking .
You are in wrong Matte. In 3rd month you will receive quickly sandbox. Off page seo need to build from begining, increase inbound links in natural logarythm. Your strategy is like: no one backlinks in first 3 months and after tons of them. You think that it look natural for search engines ?