In a significant development, Viacom has announced Yahoo! as its online advertising partner in a multiyear deal that might prove beneficial to Yahoo! vs-a-vs its younger rival, Google.

Financial terms of the deal are not yet disclosed. But Viacom will likely get 70 to 80 percent of the revenue generated from Yahoo! ads, based on existing commissions in the Internet industry.

As per the agreement, small text-based adverts will appear alongside search results and other such content on nearly 33 Web sites owned by Viacom, including MTV.com, VH1.com, ComedyCentral.com, Nickelodeon.com, and BET.com.

That Viacom and Google are embroiled in a legal tussle over copyrights issues only adds an interesting twist to the Viacom-Yahoo! association.

It was last month that Viacom sued Google over its newly acquired video sharing Web site, YouTube.com, alleging that YouTube repeatedly violates copyright law by showing clips from Viacom's shows sans permission. Viacom has demanded around $1 billion in damages from Google.

However, Google is claiming that YouTube has removed copyrighted material whenever asked, thus remaining faithful to the law.

Meanwhile, Yahoo! and Google have been competing for years now. Although Yahoo! came first, it has since been eclipsed by Google's runaway success.

Google, with reportedly a current market value of nearly $145 billion (three times more than Yahoo!), boasts advertising alliances with biggies like Time Warner's AOL.com, News Corp's MySpace.com, and IAC's Ask.com.

Yahoo! expects the latest tie to help bridge this gap. Earlier, the company introduced a new advertising formula named 'Panama' in lieu of the same objective.

Commenting on the association, Philippe Dauman, Viacom's Chief Executive Officer, said, they couldnt be more pleased to have Yahoo! as a partner, and that they look forward to growing their relationship even more over time.

Terry Semel, Yahoo! Chairman, described the Viacom deal as "the beginning of a powerful and engaging partnership between the two companies."

Google has declined to comment on the tie-up.