How can the humidity be in the minus numbers?

MIKE MOSS SAYS:    Myra,   There are different ways to represent humidity, such as absolute humidity, specific humidity, relative humidity, and using the dew point as an indicator of absolute humidity. Of all these ways to quantify the amount of moisture in the air, only the dew point can become negative, as you may have seen in a recent question here (http://www.wral.com/weather/blogpost/1201076/). Relative, specific, and absolute humidities can all theoretically be zero for perfectly dry air containing no water vapor, but they can not be less than zero.