I recently dispatched a newsletter via email. Each link in the newsletter pointed to a page on our website, and each link contained a query string that identified which newsletter a subscriber was responding to.
The query string uses Google Analytics tracking code, so the links looked something like this...
<a href="http://www.example.com/somepage.htm?utm_source=mailinglist&utm_medium=email&utm_content=may-2012" />click here!</a>
The method has worked correctly for previous mailshots, but on this occasion something rather unexpected happened. Google Analytics captured visits to the pages that were not referenced in the newsletter, in addition to the ones that were. The raw server logs also show HTTP GET requests for other unintended pages on the site, with the query string appended.
How can this be?