Google has launched a referral program as part of its AdSense advertising service. The new tab, which was added to all existing customers login in, will allow website owners to earn money by promoting the Firefox browser and the AdSense service itself.

Keen to promote its AdSense service, the search engine is offering to pay users $100 after a new user who has signed up to the service earns their first $100.

When a user you've referred to Firefox plus Google Toolbar runs Firefox for the first time, you'll receive up to $1 in your account, depending on the user's location.

Your earnings from referrals will be included with your earnings from AdSense for content and AdSense for search.

Website owners keen to make money can place one referral button per product on a given web page.

However, Google asks that publishers do not place referrals in unsolicited mass emails, software applications, or pop-ups in an attempt to earn extra cash.