Shares of real estate site Zillow fell Tuesday after the company issued a weak revenue outlook due to the later-than-expected closing of its purchase of rival site Trulia.

Seattle-based Zillow, which offers users real estate information online, closed on a $2.5 billion acquisition of Trulia in February after a months-long review by antitrust regulators.

"2015 is a transition year and we're trending a couple quarters behind where we'd like to be, due to the protracted FTC approval process which only ended two months ago," CEO Spencer Rascoff said during an update call. Still, after laying groundwork in 2015, the company expects an "incredibly bright" 2016 and 2017, he said.

The company now forecasts revenue of about $690 million in 2015, assuming that the Trulia deal had closed at the beginning of the year as was expected. Analysts have expected revenue of $740.4 million, according to FactSet.

Shares were down $2.74 at $90.20 in afternoon trading, recovering after dropping as much as 13 percent in morning trading and being halted.

Zillow will report first-quarter earnings in mid-May.