By Rex Crum, MarketWatch

SAN FRANCISCO (MarketWatch) -- Tech stocks started the week off on a mostly negative note Monday, with declines coming from many sector leaders, including Zillow Inc. after the online real-estate information company announced a $3.5 billion deal to acquire rival Trulia Inc.

Zillow (ZILLOW.XX) shares were down 3.7% at $153.20, while Trulia Inc. (TRLA) climbed almost 12%, to $63.10 after the all-stock deal that would bring together two of the biggest names in the fast-growing market for online real-estate information was announced. The deal is expected to close in 2015.

Zillow said it will continue to use the Trulia brand. Trulia Chief Executive Pete Flint will retain his title and report to Zillow CEO Spencer Rascoff. Additionally, Flint, and a second member of Trulia's board of directors will join Zillow's board.

While both companies are known mostly as resources of real-estate information for consumers, Zillow said in a statement that they "are primarily media companies, generating the majority of revenue through advertising sales to real estate professionals." In June, Zillow reported 83 million unique visitors across its mobile and Web platforms, while Trulia reported 54 million unique visitors during the month.

Mark Mahaney, of RBC Capital Markets, called the acquisition "a natural consolidation with the online real estate industry," in which advertising is valued at more than $10 billion annually.

In addition to Trulia, mild gains also came from Apple Inc. (AAPL), Priceline.com Inc. (PCLN), IBM Corp. (IBM) and Oracle Corp. (ORCL).

The Nasdaq Composite Index (RIXF) fell more than 16 points to 4,433, and the Philadelphia Semiconductor Index (SOX) was off by 0.5%.

More must-read news from MarketWatch:

Zillow to acquire Trulia in $3.5 billion all-stock deal

Why taking on more debt is the American way

Ten great Rolling Stones songs to mark Mick Jagger turning 71

Subscribe to WSJ: http://online.wsj.com?mod=djnwires

International Business M... (NYSE:IBM)
Historical Stock Chart
From Feb 2024 to Mar 2024 Click Here for more International Business M... Charts.
International Business M... (NYSE:IBM)
Historical Stock Chart
From Mar 2023 to Mar 2024 Click Here for more International Business M... Charts.