Microblogging sensation Twitter. which has now signed up more than 100 million users, outlined on Wednesday several revenue-generating initiatives, declaring that making money was now a primary goal.

The popular Internet service hopes to snag hundreds of millions more users in coming years by making the service easier, integrating Twitter directly into Web sites and focusing more on customizing the service for mobile devices.

At the company's first conference for Twitter developers on Wednesday, Chief Executive Officer Evan Williams said generating revenue was among the key priorities going forward -- a change of tone for a firm that had previously said it focused mainly on improving the user experience.

The comments come a day after Twitter rolled out a new advertising program dubbed Promoted Tweets, its first attempt to make money from its service and a milestone on the path toward an initial public offering.

Money is important, Williams said during a special talk at the event devoted to monetization. It takes a hell of a lot of money to run Twitter. There has to be a very solid revenue stream underneath this to fuel it.

But co-founder Biz Stone stressed that while the company was not philosophically opposed to floating shares to the public, he stressed that a public offering was not on the radar for the time being.

At this point we have 175 people and we just yesterday announced our revenue strategy. We're not talking about an IPO, Stone told Reuters at the event, which was attended by about 1,000 people.

While the fledgling advertising program unveiled this week now has just five advertisers in a trial run, Stone said in an interview that the company believed the new ad service represented one of the primary businesses that would finance the company's operations going forward.

We are pretty confident that this is going to work out to be a profitable, sustainable, real business for us, Stone said in an interview on the sidelines of the event, which saw Black-Eyed Peas front man will.i.am interviewed about his Twitter views.

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Twitter executive Dick Costolo also cited commercial accounts, which Twitter is currently testing with a couple hundred companies, as the second main money-making pillar.

Twitter, which allows users to send short, 140-character text messages, or Tweets, to groups of so-called followers, is one of the Web's most popular social networking services, along with Facebook and LinkedIn. The social networking services are increasingly challenging established Web players, like Google, Microsoft and Yahoo, by competing for users time online and for advertising dollars.

Twitter has roughly 105 million registered users and is adding 300,000 new users every day, the company announced at the event on Wednesday, providing official data about usage of the service for the first time.

Executives also said that 75 percent of its traffic comes from people using specialized applications created by private companies, rather than people visiting the Twitter.com site.

Still, Twitter said its site drew 180 million monthly unique visitors on its site in March, suggesting that Twitter may be more popular than previously believed. According to comScore, Twitter had 69.5 million unique visitors to its site in February.

Going forward, executives said that the company planned to increasingly target users on mobile phones.

Last week, the company acquired a one-person company that produced a Twitter app for Apple's iPhone, which will be reincarnated as Twitter's iPhone app in the coming weeks.

The company also worked with Blackberry maker Research in Motion to develop a specialized Blackberry app. Williams told the crowd that an app for phones based on Google's Android software was in the works.

Twitter sought to reassure independent software developers at the conference that the company's moves to add its own home-grown features and versions of the service would not shut out the more than 100,000 third-party programs that have been built to work alongside and enhance Twitter.

Twitter is truly a collaboration and that is not changing, said Williams.

But Stone said Twitter would continue to fill in holes it sees in the main product by developing new features and acquiring companies.

I anticipate a few more acquisitions this year, Stone said. I don't know if we're going too crazy. But there's certain things that we need to get done and we want to get done fast, and there's certain things we can take our time building.

(Reporting by Alexei Oreskovic and Edwin Chan, editing by Gerald E. McCormick and Bernard Orr)

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