My headlights work my tail lights dont?

Electrical problems on cars are the world's worst to trouble shoot. To narrow the field, I would assume the short (to ground) is caused by one of the tail lights (not to be confused with the brake, hazard, or turn-signal lights since these seem to work). I would also assume that your parking lights do not work, but if they do then the plot thickens. Normally the tail lights are interconnected to the parking lights and the license plate light. Therefore, you have 4 to 5 lights to check. The first place I would check is in the trunk to see if a tail light wire or license plate wire was not accidentially pinched or had the insulation removed. Was the car in an accident? If yes, were any lights damaged (I would check at this location)?

One word of warning -- do not exceed the fuse size for the lights. This could cause the insulation to melt in some obsure location, which you may never find.