Forum Moderators: Robert Charlton & goodroi
You will need to discover what search terms used to bring your traffic that no longer do. For this you need to analyze your server logs to see the referer information - all you traffic from clicks on Google search results will contain the information about what the search term was.
I'd say quickly grab a copy of the server logs from your high traffic time so you don't loose that historical data. Present logs will not show you what has disappeared.
It could be a penalty, a server problem, a spidering problem on Google's end, or many other things. You need the server log data to go further.
