Microsoft Corp specializes in acquiring businesses when they so small that few people notice – a very good ploy when anti-trust bloodhounds dog your footsteps, and yesterday, the company made CMG Information Services Inc an offer it couldn’t refuse for its NetCarta Corp unit: $20m cash. Redmond also agreed to take a 4.9% in Andover, Massachusetts-based CMG, which invests in, and integrates direct marketing services. Microsoft wants to integrate NetCarta’s WebMapper Web site management tool into its BackOffice groupware suite. Microsoft says NetCarta, Scotts Valley, California developer of client-server Web management and navigation tools, will give it a comprehensive intranet and Internet Web site development product. CMG’s @Ventures also has majority stakes in Lycos Inc and GeoCities, among others.