San Francisco-based PlanetRx.com Inc. (PLRX) a health care traffic and information provider in succession the Web, and San Francisco- based online issuer NextCard Inc. (NXCD) made an agreement where PlanetRx.com will exclusively market and further the NextCard Visa on its Web site. In addition, NextCard will use its clout as an online advertiser to assist PlanetRx.com through aggressive online marketing efforts. The sum of two units ...