Two Pittsburgh law firms have begun a class action lawsuit against ad technology provider DoubleClick , accusing it of serving deceptive Internet ads.

The suit, filed in a common pleas court in Pennsylvania earlier this month, accuses DoubleClick of being party to fooling Internet users with misleading ads by serving them through its DART ad serving system. The ads, which resemble computer-warning messages, represents a deceptive advertising practice, the suit contends.

"It's our understanding that DoubleClick advises their clients on strategy for increasing the click-through rate," said attorney Stanley Ference, whose law firm Ference & Associates filed the suit. "The ads are maintained on DoubleClick servers, they're served from DoubleClick, and DoubleClick controls the distribution channel."

A DoubleClick spokeswoman said the company does not comment on litigation.

The class action is a mirror image of the suit filed in November against Bonzi Software, the company that ran the ads. In that suit, Bonzi also was accused of a "diabolical scheme" of using dialog box-like ads to trick Internet users. Bonzi settled the case in May, agreeing to include the word "advertisement" in those type of ads.

DoubleClick is accused of serving more than 500 million of such ads for an unknown number of companies. The suit requests $5 per ad, in addition to $500 for each class member. The case was filed with a single representative member, Christopher Steelman, a Pittsburgh area resident. The class is defined as all U.S. Internet users who have encountered one of the ads.

Although the ads were designed by advertisers and ran on third-party Web sites, the suit contends that DoubleClick is responsible since it operates the delivery process.

"DoubleClick thus controls the advertising server process on which advertisements for its clients are located, the selection of the advertisement to be served, and the delivery of the advertisement to the user's browser," according to the complaint.

Ference said DoubleClick was not a passive participant in the process.

"They told their advertiser that they were going to do this," he said. "They informed their advertisers how to do this."

Brian Malkin, whose firm Malone, Larchuk & Middleman is also party to the suit, said class-action suits of this type served notice to companies that they would be held responsible for their business practices.

"The purpose of the lawsuit is to end deceptive practices," he said. "If DoubleClick is made to place on their ads 'advertisement,' the remedy is going to be successful."