My site I'm working on (http://www.limoboston.net) also has disappeared from the first 100 SERPs recently. The same situation as is with candis123. The site was on the first page, before I went on vacation. Now it drops the rankings. I check for penalty by typing in search box the domain name: limoboston. It comes first. Copyscape gives some 3-4 sites having similar content with one of our blog posts. The site is indexed- 216 pages. If it is because of new algo change, than what we should do? I'll very much appreciate any helpful answer.
I agree with the above answers, it could be a variety of reasons. Panda, Penguin, Competitors, etc etc etc. So my suggestion is to work to getting traffic from a variety of sources because if you rely on just seo your business is at the hand of a search engine and you could end up SOL! Variety is the key! Multiple traffic sources and multiple streams of income!
The possibility of rankings drops is the competitor works edge over your seo. When you slow down your seo or use non white hat seo your competitor will grab the position above you.
we cant decide why you loose ranking without analyzing your site there plenty of factors which we need to consider while optimizing site. your link profile, spaming links, duplicate content and so many....
new updation of august almost fluctualte 8 people out of 10...... this is the updation which google did after 8 years.. Now seo becomes more difficult and tricky...
Because google algorithm update and Your competitors are trying to grab that position and that's why one who is more relevant will rank in top search engines results.
Just make it a habit to check your Google Webmasters account to check any warnings and crawling errors.
There are many reason for drooping keywords ranking, But now is dropping because google gets some changes in Google panda.....
Now I completely agree with "andrewsmith",because SEO is a more competitive profile.You are not only the first person who have working on same keywords.Right.Anyways,First of all,start your website and competitors analysis properly,after that post an unique content on Articles and Blogs.Post any announcement about your company through Press Release Submission.I'll definitely sure,your keywords will rank once again in top 10.Good Luck.