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 32,327 websites that are Google Analytics Custom Variables Customers. We know of 9,076 live websites using Google Analytics Custom Variables and an additional 23,251 sites that used Google Analytics Custom Variables historically and 4,034 websites in the United States.
Get a list of 32,327 websites using Google Analytics Custom Variables which includes location information, hosting data, contact details, 9,076 currently live websites and an additional 63,233 domains that redirect to sites in this list. 23,251 sites that used this technology previouslyand 4,034 websites in the United States currently using Google Analytics Custom Variables.
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