gas gauge going crazy

When my gas gets low(1/4 of a tank), my gas gauge will be very eratic...it can be on full and the next time I look it will be so low that the light comes on. This is such a pain in the a$$. I hope I don't get a reply to "keep the gas above 1/4 of a tank". lol I am wondering what is wrong and how I can fix this problem. Thanks to all the reply.

My guess is the sending unit is toast in the low range or maybe (if you is lucky) there's something in the tank, possibly on the sending unit, that interupts the sending unit at low levels, like a piece of tape or Jimmy Hoffa. In my 98 Intrigue you can remove the sending unit thru the bottonm of the trunk. What's your year and model?