If you find yourself in a position where your traffic has oddly troughed to next to nothing, it’s a good idea to double check your status in the search results. If you were featuring in a certain position and now seem to be absent from the SERPs entirely, you could have been excluded from the [...]
search engine ban
A ‘natural’ link structure refers to the mix, and type, of links apparent in your site. The search engines will be suspicious of any sudden addition of large quantities of inbound or outbound links for example. This tends to indicate spamming techniques such as link stuffing as part of a link farm or such like. [...]