Custom variables are name-value pair tags that you can insert in your tracking code in order to refine Google Analytics tracking.
https://developers.google.com/analytics/devguides/collection/gajs/gaTrackingCustomVariables?hl=en
Analytics and Tracking
Get access to data on 33,308 websites that are Google Analytics Custom Variables Customers. We know of 10,318 live websites using Google Analytics Custom Variables and an additional 22,990 sites that used Google Analytics Custom Variables historically and 4,610 websites in the United States.
Get a list of 33,308 websites using Google Analytics Custom Variables which includes location information, hosting data, contact details, 10,318 currently live websites and an additional 94,685 domains that redirect to sites in this list. 22,990 sites that used this technology previouslyand 4,610 websites in the United States currently using Google Analytics Custom Variables.
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