Updated 12 March 2019 with some minor clarifications.. On 21st February 2019, WebKit announced the release of the latest iteration of Safari’s Intelligent Tracking Prevention (ITP), known as ITP 2.1. For a while now, Safari has been targeting cross-site tracking with ITP, first starting with cookies in third-party contexts, then tightening the noose after a number of workarounds emerged, and finally with the latest iteration targeting cookies that were moved from a third-party context to a first-party context.
There is a new version of this post for GTM V2 here. [Last updated June 2014] I’ve fallen in love with Universal Analytics and Google Tag Manager. Together they form an incredibly powerful tool for marketing professionals. In most cases, I no longer need to post recommendations to my client for yet another page template revision, since with the tag manager in place, I can just add custom code via the admin panel.