Google's shares edged higher today, as investors looked forward to the company's anouncement of a new social networking platform this evening.

The stock rose to $712.72 in early trading - an increase of almost 0.8 per cent - following last night's record close of $707, which sent Google into number five of the most valuable comanies in the US.

The search firm's $220 billion valuation puts it behind only Exxon Mobil, General Electric, Microsoft and AT&T, and leaves giants such as Bank of America, Proctor and Gamble and Citigroup trailing in its wake.

Tonight, executives will give details of Google's new social networking platform, OpenSocial, which will usher in a period of unprecedented compatability between social networks.

There have also been reports that the company is in talks with American mobile operators, including Verizon, about enabling phones which will be powered by its highly anticipated mobile operating system to run on their networks.

Details are expected to be announced in a couple of weeks.

Speculation about Google's plans in the social networking and mobile arenas have prompted a period of unprecedented investor confidence in the company, lifting the shares from under $500 since August.

The stock has risen by 20 per cent in the past month, and has increased its value more than eightfold since the company went public three years ago.

Analysts say that investors appear to be have brushed aside concerns about the slowing growth of online advertising and Viacom's $1 billion lawsuit against the company, and instead focused on Google's confidence - expressed in a recent earnings call - that it can expand its core online ad sales.

This evening at its headquarters in Mountain View, California, Google will outline plans which will enable software developers to write applications which are compatible with a range of different social networking sites, including Google's own Orkut.

The company is keen to keep in check its young rival, Facebook, which has seen more than 5,000 applications built by developers - and downloaded by millions of its users to their 'profiles' - since it opened its platform in May.

It also wants to seize back the initiative from Microsoft, which last week thwarted Google's ambition to serve the ads on Facebook's platform when it paid $240 million for a 1.6 per cent stake in the networking site, expanding the two firms' existing relationship.

Google is hoping that a cross-site, open platform will be of greater appeal to developers than Facebook, and that the move will generate renewed interest in Orkut, which, whilst popular in Brazil, has struggled to gain a foothold in the US.

Two weeks ago, Google reported that its profit for the third quarter rose to $1.32 billion - an increase of 46 per cent from a year earlier, and executives were bullish about the possibility of growing its sales of online display ads, such as 'banner ads', as well as extending its operations into print, radio and television advertising.

Analysts said that Google's core search business was so large that it had "enormous latitude" to experiment in the mobile market, which, along with social networking sites, is seen as one of the main areas for advertising platforms such as Google's to colonise.

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