1. A computer-implemented method of executing a plurality of live content usage experiments, comprising: providing at a content server a unique identification tag to a content requesting client computing device; processing at the content server the unique identification tag upon receiving a request for content from the client computing device at the content server to verify if the client computing device is a test subject; offering at the content server non-experiment content to the client computing device; offering at the content server experiment content to the client computing device only if the client computing device is verified as a test subject; tracking content usage at the content server of experiment content and non-experiment content offered to the client computing device to produce content usage data; and analyzing the content usage data to compare usage of experiment content versus non-experiment content to determine if experiment content was used more often than non-experiment content.