DALLAS (AP) - Chocolates are always nice, and a diamond necklace would be delightful. But a Dallas-based ministry thinks it has a better idea for Valentine's Day. "Her gift for Valentines? Stop looking at porn," proclaim billboards put up by NetAccountability, a nonprofit software company that aims to help Christians confront the "secret sin" of pornography. If national surveys are any indication, it is a personal battle waged by millions of Christians. Almost 18 percent of people who called themselves born-again Christians admitted visiting Internet porn sites, according to a 2000 survey of 1,031 adults by the evangelical group Focus...