A former bear has turned bullish on Google ( GOOG) as Internet advertising shows signs of stabilizing.

Merriman Curhan Ford analyst Richard Fetyko, who initiated his coverage on Google with a sell rating in November, then went lukewarm with a neutral in January, upgraded the stock to a buy Tuesday.

Fetyko bases his newfound optimism on a brighter view of the Internet search market. "We are seeing an improvement in search ad spending and pricing," says Fetyko.

Google shares are down 42% from a $602 high in May after a severe economic downturn stunted the Internet advertiser's sales growth. But Internet advertising spending may be starting to thaw, says Fetyko.

"After a weak January and February, search ad spend and pricing appear to have stabilized or even increased in March," Fetyko wrote in his report Tuesday.

Fetyko also cited potential in mobile search -- a big new market outside the desktop search, which Google already dominates -- because as Research In Motion's ( RIMM) BlackBerry phones and Apple's ( AAPL) iPhone become more popular, more people are using the 3G-powered devices to make queries on the Google search engine.

Google shares were rising $7.82, or 2.3%, to $350.51 in early trading Tuesday.

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