Tell me why this happened

Ok, so today for a fun counter top science experiment, I decided to try making Hydrogen gas though electrolysis. I put some salt (table salt, NaCl) into water and stirred it in, then got a 6v battery back and attached the ends with clips to graphite leads.
The setup started to produce bubbles of gas. I let it sit for a few minutes until i noticed that the water was turning a yellow color and there was a dark solid accumulating on the bottom. What exactly happened? Some chemical reaction that i did not expect to happen.

You're using graphite as electrodes, there's probably a reaction occurring on the cathode or anode causing a reduction to happen making your new yellow substance.

It was probably chlorine, but I don't know why it would sink...