Google, Microsoft and Yahoo! are the most important and powerful Internet companies of the world! They will be rivals forever, but business is business and from to time to time they must become friends and join forces.

For example, the three major companies announced yesterday that they decided to pay a combined $31.5 million fine to settle federal civil charges alleging they had accepted ads promoting online gambling, which is illegal in the United States. Although all the three companies said they stopped taking those ads long time ago, they agreed to settle the case. Negotiations have been going on for more than a year.

The United States attorney for eastern Missouri Catherine L. Hanaway announced the settlement yesterday, when she added that the investigation conducted by her office, the Internal Revenue Service and the FBI dated to 2000.

Microsoft was set to pay a $21 million part of the fine, which includes a $4.5 million forfeiture, $9 million in public service ads over a three-year period (starting 2008) and $7.5 million to be paid to the International Center for Missing and Exploited Children.

Online gambling is illegal and this will be the message of the public service campaign Microsoft will sponsor. “We’re hopeful that our educational campaign will stop young people from gambling before they start,” the world’s largest software maker said in a statement.

Yahoo will have to pay $7.5 million, which includes a $3 million forfeiture and $4.5 million in public service ads over the next three years, while Google will pay only $3 million.