Shares of ValueClick lost nearly one quarter of their value Monday after the company lowered its 2007 guidance and announced second-quarter results that fell short of Wall Street expectations.

ValueClick reported net income of $18 million (17 cents per share), a 22 percent increase from the same period a year earlier. Analysts surveyed by Thomson Financial were expecting 18 cents a share.

Revenue for the Westlake Village-based online advertising firm rose 14 percent to $149 million. But that was well short of Wall Street’s forecast of $159 million. The shortfall was due to declines in the promotion-based business, the company said.

“The promotion-based sector suffered a downturn that began in late May and became more pronounced in June, which negatively impacted our quarter,” said Chief Executive Tom Vadnais.

The company also lowered its full-year earnings guidance to between 74 cents to 76 cents per share on revenue of $645 million to $660 million. ValueClick previously said it expected earnings of between 79 cents and 81 cents a share on revenue of $655 million to $665 million.

All of this comes less than two weeks after the company said it is buying comparison shopping Web site company MeziMedia for up to $352 million. It also comes as shares of ValueClick were boosted earlier this year after Google, Microsoft and Yahoo all bought online advertising firms which led investors to bid up shares of ValueClick thinking it would be the next to be acquired. No deal happened.

Shares in ValueClick plunged 24 percent to $19.76 in afternoon trading Monday on the Nasdaq. Shares are down more than 48 percent since hitting a 52-week high of $36.70 in May.