Google is rolling out new referring URL format for Google search. Up to now, the usual referrer for clicks on Google search results for the term say "flowers", would be: http://www.google.com/search?hl=en&q=flowers&btnG=Google+Search

Now it will be like this: http://www.google.com/url?sa=t&source=web&ct=res&cd=7&url=http%3A%2F%2Fwww.example.com%2Fmypage.htm&ei=0SjdSa-1N5O8M_qW8dQN&rct=j&q=flowers&usg=AFQjCNHJXSUh7Vw7oubPaO3tZOzz-F-u_w&sig2=X8uCFh6IoPtnwmvGMULQfw

The key difference between two urls is of "/search?" and the "/url?". Google Analytics does not depend on the "/search?" string, but other analytics packages may need to adapt to this change in our referrer string to maintain accurate reports, announced Analytics blog.