Shares of ValueClick took a tumble Tuesday after the company said sales would be lower than expected for both the third quarter and the full fiscal year due to weakness in its online advertising lead generation business.

For the third quarter, Westlake Village-based ValueClick now expects sales of $156 million to $157 million, down from prior guidance of $155 million to $165 million. The company reaffirmed third-quarter earnings guidance of 16 cents to 17 cents a share. Analysts polled by Thomson Financial had expected earnings of 17 cents on revenue of $159 million.

ValueClick shares were down $2.75, or 10 percent, to $25.03 in midday trading on the Nasdaq after a 12 percent fall earlier in the morning. Shares had gained more than 40 percent over the past month amid speculation that the company could be a takeover target.

The disappointing results in the lead generation segment were partially offset by better than expected revenue in its comparison shopping business, the company said.

For the full year, the company now expects sales of between $635 million and $640 million, down from earlier guidance of $645 million to $660 million. Analysts were expecting $650 million.