I forget what that means. Bad ground? What should I check for?

Have you looked at Wes Vann's tech ref section? He has a check-out procedure in there for fuel gages.
1, An open ground to the meter
2, Open sender lead
3, Open sender ground
One of these is most likely the cause.

http://www.chevelles.com/techref/ftecref18.html

Thanks guys. I found out my 1960 has a 0-30 ohm sending unit. I'll hit it as soon as I go to Home Depot and use my gift certificate to buy a multi-meter.

I work in the dark sometimes on your 60 'cause I don't have much in my material to cover that car. Cars in those days didn't have a separate ground lead to the fuel gage. They relied on the dash ground. Some of the dash grounding schemes weren't the best. The 64 Chevelle relies on a copper strip that goes through the lighter, ignition switch, and gets tied to ground through the original radio mounts. What I did on mine is run a separate ground strap from the instrument cluster, metal in those days, down to the metal dash frame. Stopped a lot of the intermittent dash ground problems.