It started one evening when I turned on the lights, and the dashboard light did not work, I had to use a torch to see the speedo.

Then I noticed that the front headlight (passenger side) was not working, I replaced it. then one of the rear lights (the inner one of the two) passenger side was not working. I replaced that too.

Now, the problem has moved to the Rear lights on the drivers side, (the inner light does not work, and the bulb is fine), and when you put your foot on the brake, the break lights come on, and the one on the drivers side goes off.

I checked the fuses, they all seem ok
I checked the bulbs, they seem ok

Somebody said it was the earth, do you think it could be and how would I check this and fix this.

Incidentally this happened a few weeks after I had a stereo put in, and it worked ok so I dont think this is the problem, but I am not ruling this out.