Web Master:
The bottom fronds of a palm will die naturally, if they are lowest leaves and the rest of the plant looks healthy I wouldn't worry about it. If that is the case just cut off the dead fronds. The main thing is that the growing tip is looking healthy.
The most common problem with house plants is over watering, it may be that you need to reduce the times you water during the colder months, always a good idea to allow the soil to become quite dry between waterings.