Honda 1999 Civic Sedan Reference Owner's Manual page 55

Indicator Lights
U.S. D X , Value Package, and Canadian LX
Instruments and Controls
Seat Belt Reminder Light
This indicator lights when you turn
the ignition switch ON (II). It is a
reminder to you and your passengers
to protect yourselves by fastening
the seat belts. A beeper also sounds
if you have not fastened your seat
belt.
If you do not fasten your seat belt,
the beeper will stop after a few
seconds but the light stays on until
you do. Both the light and the beeper
stay off if you fasten your seat belt
before turning on the ignition.
* Differences in the indicators for
Canadian models are noted in the
text.