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 22,720 websites that are Google Analytics Custom Variables Customers. We know of 4,204 live websites using Google Analytics Custom Variables and an additional 18,516 sites that used Google Analytics Custom Variables historically and 842 websites in the United States.
Get a list of 22,720 websites using Google Analytics Custom Variables which includes location information, hosting data, contact details, 4,204 currently live websites and an additional 8,245 domains that redirect to sites in this list. 18,516 sites that used this technology previously and 842 websites in the United States currently using Google Analytics Custom Variables.
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