Google Inc. has agreed to pay up to $90 million to settle a lawsuit alleging the online search engine leader overcharged thousands of advertisers who paid for bogus sales referrals generated through a ruse known as "click fraud." The proposed settlement, announced by the company Wednesday, would apply to all advertisers in Google's network during the past four years. Any Web site showing improper charges dating back to 2002 will be eligible for an account credit that could be used toward future ads distributed by Google. The total value of the credits available to advertisers will be lower than $90 million because part of that amount will be used to cover the fees of lawyers who filed the case last year in Arkansas state court. The proposed settlement still requires final court approval. The lawsuit, filed by Lane's Gifts and Collectibles on behalf of all Google advertisers, revolves around one of the most sensitive subjects facing Google and Yahoo Inc., which runs the Internet's second largest marketing network.