Welcome to WebmasterWorld Guest from 18.104.22.168
"Losing" a site can be a painful and frustrating experience. I want to collect links for our best references in one spot -- those threads that can give you ideas of things to check and what you can do to address the situatrion once you identify a potential problem.
The following three address both drops in rank, where some small amount of search traffic remains, and the a complete disappearance from the index with the resulting no search traffic.
Feel free to reply to this thread -- I will edit out side comments in the future so we end up with a nice, concentrated "Library quality" thread.