Dive Summary:

• With Apple's recent iOS 6 upgrade to iPhones and iPads, its Safari browser has begun routing Google searches made from its search box to an encrypted version of Google search, causing the referrer header not to be passed on at least some occasions.
• In these cases, the destination site loses the ability to track the search terms that users entered before arriving.
• The encryption does, however, provide some privacy protection for users.

From the article:

Another source of Google search referrer data appears lost. Searches through Google that happen in Apple’s Safari browser search box in iOS 6, Apple’s latest mobile operating system, no longer pass along search terms to publishers.

For those unfamiliar, “referrer” data is information a browser passes along to a publisher about the last page you were on. When you do a search on a search engine, this means what you searched for — the exact words — are passed along as part of the referrer. ...