Ever since I was little and living at home with my parents I, my sister and brother have always seen a drip coming from the left corner of door ways. I have at times been so convinced that I have had to touch the ceiling to make sure there wasn't a leak. (the ceiling and the surrounding area are always bone dry). I still see the drip fro time to time now in my own home and my brother and sister still see it in there own homes. What is it?

What do you mean by a drip? Like liquid dripping out of the door frame, or out of the ceiling??