You've just experienced one of those glorious one-night stands you read about in fairy tales like the "Sex and the City" columns of yore. But the morning after ... well, let's just say things aren't exactly coming up roses. Where do you turn for safe, comfortable, confidential STD testing and treatment? San Francisco City Clinic, of course. This year the clinic is celebrating 100 years of zapping not just simple post-tryst maladies, but more alarming epidemics as well. From the "red plague" of the Barbary Coast (syphilis) to the devastation of "gay cancer" (AIDS) and beyond, the capable city clinicians — trained through the San Francisco Department of Public Health — have fought back against STDs in an honest, shame-free environment. Free and low-cost diagnosis and treatments are a priority; promoting healthy sex while protecting against transmission and outbreaks is the mission.