It looks like double trouble ahead for DoubleClick (DCLK) .

Wednesday's market action saw the Net ad firm's stock plunge as much as 20%, matching the action in Net juggernaut

Yahoo!

(YHOO)

. Investors sold Net stocks early and often on fears that the dot-com ad shakeout, illustrated most tellingly by an unexpected third-quarter decline in advertisers on the Yahoo! site, will drive a steep drop in earnings and revenue growth at ad-supported companies.

With DoubleClick scheduled to report third-quarter earnings Thursday afternoon, the prospect of more bad news about an already thinning Net advertising market looms. Even a strong report isn't likely to ignite a rally in the stock, investors say, noting that the recent selloff signifies a greater dot-com queasiness this fall.

Jitters

Like fellow Internet ad-supported top dog Yahoo!, DoubleClick is falling victim to a market that's nervous about all things dot-com. Like Yahoo!, DoubleClick has seen its stock plummet below its 52-week lows after a giddy high at the turn of the year. DoubleClick, which reached a split-adjusted $135.25 in early January, fell $5.31, or 21%, Wednesday to $19.38. Yahoo!, meanwhile, dropped $16.38, or 20%, to $66.31.

Doubling Down
DoubleClick shares' precipitous slide

And like Yahoo!, which got

hammered in after-hours trading Tuesday night despite

beating revenue and earnings estimates, DoubleClick could find that meeting analysts' numbers won't help a stock if it isn't promising rapid relief from the dot-com ad drought.

That said, DoubleClick has a lot going for it: The company has emerged as the clear leader among the firms that deliver advertising-related goods and services to other companies on the Net, primarily by selling advertising on behalf of numerous Web sites. It's pulling ahead of rivals such as

24/7 Media

(TFSM)

and

Engage

(ENGA)

, bulking up in part by making deals to acquire smaller ad firms like email marketer

NetCreations

TheStreet Recommends

(NTCR)

and research firm

@plan

(APLN)

.

And the Internet advertising market in which DoubleClick operates still looks like a winner over the long haul, though a dot-com spending pullback has crimped online advertising's growth over the past few months.

Expectations

The Internet advertising firm is expected to report earnings of 3 cents a share, reversing a year-ago 7-cent loss, according to analysts surveyed by

First Call

.

Revenue is expected to amount to about $135 million for the quarter, or $154 million in "systems" revenue (an additional figure that DoubleClick releases in order to spotlight the extent of the work it does for client

AltaVista

).

Beyond the headline numbers, investors will be looking at statistics relating to DoubleClick's three lines of business, says Dana Serman, research analyst at

Lazard Freres

-- how the firm's ad sales, or media business is holding up; the performance of its technology segment revolving around its DART ad-serving business, and the data business built on its

Abacus

acquisition, where the third quarter is traditionally the strongest of the year.

Sermin says he thinks the company could meet or beat his expectations. And he also thinks that DoubleClick, which is slowly catching up to Yahoo!'s revenues, could eventually narrow the market cap gap between its $2.4 billion and Yahoo!'s $36.4 billion. (Serman, whose firm hasn't done underwriting for Yahoo!, has a buy, Lazard's highest rating, on the stock.)

But Serman isn't banking on a miracle recovery for the stock following the earnings call. "This market environment is such that even good news does not serve as a catalyst for the upside," he says. He points out that because of the boom in dot-com fueled Internet advertising at the end of 1999 and the beginning of 2000, it will take until the second quarter of 2001 before Internet advertising companies will have an easier time impressing investors with year-over-year comparisons.