Microsoft has increased its rivalry with Yahoo! on the classified job front. This week the software maker expanded its online ad presence by taking an equity stake in CareerBuilder.com, according to a New York Times report.

Microsoft will own about 4 percent of CareerBuilder, which is also owned by the Tribune Company, Gannett Company and McClatchy Company.

The deal allows Microsoft's MSN to keep CareerBuilder as its exclusive job search engine through 2013.

"It has been a great relationship for us," said Steve Berkowitz, senior vice president for online services at Microsoft.

CareerBuilder competes directly with Yahoo's HotJobs property. Yahoo recently struck a deal with several hundred newspapers, including McClatchy, to share advertising and editorial content.

In the meantime, possible merger talks between Yahoo and Microsoft appear to off.

Yahoo boss Terry Semel spoke at Microsoft's advertising summit, but gave no indication that a deal was in the works. Instead he spoke about shaping online advertising, while taking the time to chastise Google for YouTube's copyright woes.