You probably have a
But if your site had a steady ranking (for a longtime) for a specific keyword phrase and suddenly the usual ranking drops ten or twenty pages, then this also sounds like a penalty.
But to be certain about this, first do some other ranking checks and visit the most important Webmaster forums and blogs, read some daily SEO feeds to see if this signal has happened to others too. Sometimes during a
A new algorithm implementation can also have this effect.
But if there is no explicable reason for a large drop down (or a removal from the index) of your ranking, then you should think about a possible penalty.
The first thing you should NOT do is contactingimmediately.
If you have aWebmaster account then they probably will contact you with a message if your site has been manual excluded from the index.