Place the tracker in links to yours and other hubs from outside of HubPages.
When someone visits any hub you have referred them to and clicks on advertising, you will receive a percentage of the adsense revenue.
When people sign up for HubPages after clicking on your referral link, you will get a percentage of the revenue share on their hubs.
URL trackers allow HubPages "track" your referral.
http:// hubpages.com/_yourtracker / hub/ a-hub/