Google Tag Manager

Google Tag Manager is a free tool from Google, designed to make it possible to track different events through ‘tags’, snippets of code which pass data about particular browsing behaviour or events for greater segmentation and personalisation. The Google platform isn’t necessarily as thorough as other tag tracking and management tools, but the free package is suitable for most users looking to make more intelligent use of tags to personalise the user experience.

http://www.google.com/insights/tagmanager/home