One of the biggest fears for web site owners that have long relied on search traffic for new business is a sudden drop in search engine rankings.  Some webmasters are experiencing this very situation as a result of Google's recent Mayday update ( Matt Cutts video ). In most cases, it takes a lot for a tenured web site to mess up it's search visibility.  In other situations, it doesn't take much at all. Avoiding mistakes that result in exclusion,