Stereo & Electronics - Need help with my Tail light!

I just notice today that when i step on the breaks, my driver side tail light doesn't go on. If i turn on the lights, it does go on, it just doesn't get brighter when i apply the brakes.

i've always thought that cars with only one tail light working look pretty ridiculous (if anyone of u are driving aroud like this...sorry dont mean to offend)...so now that it is happening to me, it is really bugging me.

Anyone one know what can be wrong, and what i can do to fix it?

Any info will be appreciated...Thanks

Replace the bulb.

The bulbs are dual filament. The bright filament has burnt out and the dim filament still works.