Fans of Linux, Microsoft and Macs used to be able to search for information about those topics on Google using specialized search tools that narrowed the results to a focused set of highly relevant Web sites. Earlier this week, however, it was discovered that Google has pulled the plug on many such specialized search portals–including Google.com/linux, Google.com/microsoft, Google.com/mac and Google.com/bsd–redirecting users to Google.com/webhp instead.