A former manager of program acquisition at HBO, Warner moved rapidly up the cable corporate ladder to become vice president of HBO Enterprises. In that capacity, Warner was responsible for worldwide distribution and sales of HBO programming to ancillary markets, negotiated domestic and foreign co-production agreements and oversaw marketing of both "Selectiones en Espanol" (selected videos in Spanish) and the library of Time-Life Films. In 1989 he moved to CBS as president of CBS Enterprises, a division of the CBS/Broadcast Group created to govern CBS Broadcast International, CBS Video and other distribution arms of the company. In April 1995, Warner was named president of CBS Television Network which entailed overseeing such areas as CBS Affiliate Relations, CBS Network Sales and CBS Advertising, Marketing and Promotion, as well as overall responsibility for CBS Enterprises. With the departure of Peter Lund in May 1997, however, the network restructured its executive levels and Warner's position was effectively eliminated in August of that year. He agreed to remain with the network for several months in an effort to oversee a smooth transition of power as Leslie Moonves assumed responsibilities as president, CBS Television. By January 1998, however, he had found a new position, as president of Primedia Magazine Group, overseeing such publications as SEVENTEEN and SOAP OPERA DIGEST. Warner moved on to run Third Floor Enterprises, a digital consulting firm that created Internet strategies for clients like fashion designer Tommy Hilfiger. In January 2000, he was hired as president of iballs, a digital marketing company.