Gas gauge is not reading correctly. It reads correctly every now and then.

What is your question?

I have a 1997 Ford Taurus and the fuel gauge is not reading right. When I start the car up it reads below the empty mark. When I start to drive down the road the fuel gauge will go up past the empty mark and stop at the quarter of a tank mark then i will go back past the empty mark and read its low on fuel and stays there. Can someone please help me out.