FACTBOX-Mergers in the Web advertising sector

By Paul Thomasch

(Reuters) - Microsoft's (MSFT.O) $6 billion (3 billion pound) purchase of aQuantive AQNT.O on Friday is the latest of a string of deals in the rapidly consolidating online advertising industry.

AQuantive, which helps advertisers target online ads and offers Web site development services, is Microsoft's biggest acquisition to date. At $66.50 a share, the deal represents an 85 percent premium to aQuantive's closing price on Thursday.

Here is a look at some other transactions in the sector:

December 20, 2006 - French advertising group Publicis (PUBP.PA) announces deal to buy Digitas for $1.3 billion in cash, or $13.50 a share, representing a 23 percent premium to its closing share price the previous day.

An interactive and direct-marketing firm, Digitas' clients include American Express, General Motors, Home Depot and Time Warner. The company, based in Boston, had an estimated 2006 revenue of around $400 million.

"We were missing a major step and it's now happening," said Publicis Chairman and CEO Maurice Levy.

April 13, 2007 - Google (GOOG.O), in its biggest acquisition, says it will pay $3.1 billion for DoubleClick from majority owner Hellman & Friedman. Less than 2 years ago, the private firm had paid around $335 million for the assets Google wants.

Founded in 1996, DoubleClick offers a digital marketplace that connects ad agencies, marketers and Web site publishers. It also specialises in the Web display ad market, which includes richer graphic and online banner ads for corporate brands.