Google has agreed to settle a lawsuit filed by online store Lane's Gifts and Collectibles accusing the search giant of 'click fraud'. 

Under the settlement, Google has promised to revise the terms and conditions of its AdSense pay-per-click advertising programme.

Google had previously forced advertisers and publishers to file click fraud reports within 60 days, but has now abandoned this filing window.

This means that advertisers can challenge advertisings dating back to 2002, when Google first launched AdSense.

Advertisers that successfully challenge past clicks will receive credits that they can apply to the purchase of new Google ads.

The search firm was unable to predict how much money advertisers could end up reclaiming. The total cost of the settlement including attorneys' fees is capped at $90m, according to Google. The settlement has yet to be approved by the judge presiding over the case.

Click fraud occurs when a person or automated script clicks on pay-per-click advertisements for financial gain.

Perpetrators are typically competitors trying to increase the cost of a rival's marketing campaign, or website operators attempting to increase site revenues.

Click fraud is controversial because Google benefits from the scam through the commissions charged for the advertising plans. Critics have suggested that this gives the search firm an incentive to turn a blind eye to the practice.

Google won a lawsuit in May last year against the Auction Experts website, which the search company alleged had raked in $50,000 by hiring individuals to click on advertisements on its website. Google was awarded $75,000 in damages.