NEW YORK (

TheStreet

) --

Yahoo!

(YHOO)

slumped 0.48% to $15.57 despite the news that Marissa Mayer was

appointed

CEO. Mayer is Yahoo!'s third CEO in just the last few months, following the ousted Scott Thompson and interim CEO Ross Levinsohn.

The announcement has heightened investor interest in Yahoo!'s

second-quarter earnings

released after market close on Tuesday.

Cisco Systems

(CSCO) - Get Cisco Systems, Inc. Report

dropped 0.79% to $16.06 on Tuesday. The company announced the acquisition of privately held, security software firm,

Virtuata

, on Monday.

"Together, Cisco and Virtuata will enable consistent and enhanced security for virtual machines allowing customers to accelerate the deployment of multi-tenant, multi-hypervisor cloud infrastructures," Cisco's Head of Corporate Business Development, Hilton Romanski, wrote on the

company's blog

.

Facebook

(FB) - Get Facebook, Inc. Class A Report

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tumbled 3.03% to $27.39 after

Capstone Investments

released a report revealing a 11%

decline in US users

over the past six months. Facebook shares also declined sharply at the end of Monday.

Zynga

(FB) - Get Facebook, Inc. Class A Report

, which generates a significant portion of its revenue from Facebook gamers, fell sharply on Tuesday, plunging 6.83% to $4.50.

--Written by Nathalie Pierrepont in New York.

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