InformationWeek reports Google is again being sued — this time, because of a box in the AdWords buying process.

The box enables advertisers to enter a maximum CPC bid. Its purpose is to help companies keep a tight rein on ad spend, but advertisers that leave the box blank are apparently enrolled in the CPC program anyway.

"Google does not inform its advertisers that if they leave the content bid CPC input blank, Google will use the advertiser's CPC bid for clicks occurring on the content network," alleges the suit, filed by Kabateck Brown Kellner, LLP on behalf of David Almeida in the US District Court of San Jose, CA.

"Google does this despite the fact that ads placed on the content network are demonstrably inferior to ads appearing on search result pages."

The plaintiff seeks class action status for AdWords customers that left the box blank.

Kabateck has a history of pursuing major tech brands on behalf of aggrieved advertisers and customers. In March it sued Apple for failing to disclose that its new 20-inch iMacs are technically inferior to previous generations. It has also raised click fraud suits against Google and Yahoo.